I think I have a few answers...
Samantha was right when she said that the "goold old days" never existed; they didn't. Even Socrates was quoted as complaining about how the youth didn't respect their elders over 2000 years ago. The most you can do is chart the patterns of behavior.
Part of the allure of the old days is that there was a great deal of functionality involved in parenting...but it came at a cost. Keep in mind that the culture that bred the hard-working respectful kids also thought a belt superceded an intelligent conversation, and also would have perceived us as deviants who should be locked up or institutionalized to protect society. So yes, the "good old days" did work because everything else was sublimated or repressed. It was not a culture that could deal or tolerate complex issues, and the men especially couldn't handle emotion very well, and the "daddy issues" have become so legendary that entire plot devices of great novels revolve around the estranged son-father/mother-daughter dynamic.
I think the modern incarnation of disrespect that Artoo mentioned has to do with a combination of corporate culture and extreme shelteredness.
CORPORATE CULTURE
With the corporation gaining almost god-like powers over the last 3 decades and driving the technology market that has come to overwhelm almost every other legal market except fuel, the competition that was once considered the character-building trait of champions in the old days created a resurgence in the Guilded Age Era monopolistic greed. And to make things worse, the pursuit of market domination made the business world a competition to see who can make the most money. High-ranking business people make more money than they can physically spend in a lifetime and yet, they ALWAYS NEED MORE. In order to obtain more, they adopted new retail policies that catered to every whim a customer could have, especially in the vein of returns and discounts; they gave new meaning to the phrase "THE CUSTOMER IS ALWAYS RIGHT." The result was that an entire generation of customers learned that a business would give them anything they want if they bitched hard enough, and that's become an almost psychopathic habit amongst them.
Ask anybody who's ever worked retail if theere's a difference between children and adults (especially at Christimastime) and they'll tell you the parents are often worse. The public has been able to channel their life frsutrations into the work world where the employee has now become a serf. The modern culture, in pursuit of financial excellence has actually REGRESSED the public population into a type of mass infantalism, where bitching and whining get you what you want, and if it doesn't, then it's THEIR FAULT not yours and you can exploiut the company's fear of losing customers to get the offending employee in trouble.
SHELTEREDNESS
The better life gets, the more sensitive we become...which is a good thing when you consider the nearly psychotic behavior ancient societies used in interpersonal relationships of everyday life (the great Hebrew leaders of the Bible were psychopaths; they used the same brutalization techniques in their campaigns as warlords in Third World countries use today). A lot of old school "get your hands dirty" philosophy comes from rural-pioneer hardscrabble living where arbitration laws hadn't been established or weren't well-enforced. But arbitration showed that life doesn;t fit into neat little ordinances built for it, and soon arbitration gave way to micromanaging, where the key focus was in establishing culpability for damages or penalties. if you ever hear anybody say "TAKE SOME RESPONSIBILITY!" tell them "FUCK YOU!" because they aren't talking about responsibility, they're talking about the bill and who's gonna foot it, and you'll find those same people very slippery about their own "responsibility" when they find thmselves in those positions.
THAT'S WHY SO MANY PEOPLE ARE APATHETIC...YOU CAN GET IN TROUBLE FOR TRYING TO DO THE RIGHT THING THESE DAYS SIMPLY BECAUSE YOU DON'T HAVE OFFICIAL RESPONSIBILITY. So why bother helping people when it might likely cause you more trouble than you want?
Alongside of it is the growth of stability, which peaked in the 1950s; the post-WWII ecomomic boom created with it a religious zeal for the perfect life, where everything was fine and dandy. Don't laugh, people bought into this enough to think that it was real and that we can get there today by going backwards. With this was the realization amongst the baby Boomers that a great deal of society still fucntioned at the expense of other classes, marked by race or religion--an ideological inconsistency of the American Way of Life that their parent generation considered a practical exemption--and set out to change that and many other traditional notions that, while functional, were simplisitc and not sufficiently verasatile.
Combine the first two with this one and now you have a cultural shift that idealizes prosperous harmony and uses arbitration to micromanage people's everyday lives. Mutations start to emerge that rewrite the code of social behavior WITHOT changing the cultural template upon which it's based.
So in other words: We're trying to dissuade people from practicing aggressive, confrontational tribalist behavior without actually realizing that aggressive, confrontational tribalist behavior is the very attitude upon which the American infrastructure is BUILT! We've created a philosophy with no practical application in our society so it has nowhere to go but into whatever avenues it can squeeze.
Road rage is the perfect example. People who get road rage aren't really mad at the person they lash out at, they're mad at the people creating the situations they can't escape from or change because the only viable options aren't allowed to work (your co-workers/boss might think twice about stealing your lunch if you broke his nose, but you can't do it legally so nothing changes and you stay trapped). The ceaseless stress, combined with pressure to succeed and outperform and physical exhaustion due to the ridiculous work ethic disrupt cerebral stability and impulse control flies out the window. The other driver is simply the person IN THE WAY of you doing the thing you need to do to get the other people you can't control off your back. You see the same dynamic in absuive homes: husband hits wife, wife hits kids, kids hit the pet. It rolls downhill.
Now, where does this fit into the pushy teenager? Think about it: he's a young man with a strong sense of entitlement who needs to be places fast for immediate gratifcation and someone else has the nerve to interfere with that...does that sound like a personality borne of the combined paradigms I just described above?
On a final note, I would also add that another habit as old as that of the young having no respect for their elders is that a large part of parenting is dependent on ignorance. It starts out when they're young and incapable of undertanding the concepts you're trying to explain to them (children dont usually dvelop a sense of dimension until 3 years of age), so you take advantage of their ignorance to control their disruptive impulsive behavior. Problem is, this practice extends into adolescence and then you start exploiting their ignorance so they don;t learn more than you know earlier than you'd like; the old school parents also feel that they should decide what and how their children think, believe, and feel so that doesn't help. So children at large have no realistic idea of how the real world works. A grown man would know that you can't win every fight and that picking a fight over a cab is asking for more trouble than the fare is worth...teenager doesn't exactly realize that, especially a teenager who models his behavior off of a pushy culture that feels it can get what it wants by stepping on people who get in it's entitled way.
Teenagers also have the benefit of knowing that most people avoid direct confrontation and can be intimidated easily; and if that person CAN'T be easily intimidated...they CAN be easily sued courtesy of the culture of micromanagement I mentioned earlier.
