she has very sensitive soles, which is why her shoe ended up on the floor. lol

There have been conversations going on lately about involving unsuspecting people in your fetish, and I am in fact against encouraging people to do things like this.
The truth is that nobody is here on this Earth to fulfill your sexual fantasies. They are not "opportunities" waiting to happen. Nobody who is otherwise not already attracted to you or knows you is asking for your attention.
If somebody with a tickling fetish can tickle people for fun, indiscriminately or not based on attraction at all, TRULY just for fun, and a person ACTUALLY also finds it fun, then maybe there's no wrong being done.
But no amount of self-talk that going out of your way to disguise sexual intentions makes it any better, respectful or LEGAL. Some of this is REALLY bad, irresponsible advice to delude YOURSELF, and possibly humiliate and hurt somebody.
Zeezil suggested to "do it intentionally, and look the person in the eyes" and "You want to show that you're deliberately doing something playful and funny to them, NOT sneaky or creepy".
Unless you really are being playful and funny, you'd still be doing it for stimulation. Who are you really trying to fool, this other person or yourself? Pretending that you're doing it for fun, doesn't make you any less of a creep.
I can't say this for a fact in your experiences, but likely if you've been using these "opportunities" ever since to tickle people, you probably offended, hurt or lost the trust of many of them over the years who never told you.
Say all you want that you know the person and you're just "playing". There's a thin line between that and harassment if a person doesn't recognize your game as purely fun.
Many cases of people who harass people sexually actually involve them taking advantage of an established, reputedly close and friendly relationship with a person to get away with copping a feel. Often in relationships involving even minimal physical touching, a person may do something inappropriate, and try passing it off as "just a joke", accidental, or thought to have been desired. Some predators start a habit of touching a person just to try to get away with that.
Eliminating boundaries between them and a person's body also gives a predator the opportunity to try to control someone emotionally, in which case much worse things can happen.
So for good reason, uninvited touch can threaten and greatly offend some people, and it's very mistaken to think that violating those boundaries is unharmful.
Unless you and another person are on the right terms for to flirt or play with no offense taken, don't needlessly touch people.
It would probably be LESS creepy to just be upfront about your attraction to a person you're on good terms with, or even your admiration of their body. A lot of people would rather you leave them alone once they know that your intention is to flirt with or touch them. But if they're okay with the admission of this, maybe you're in the clear.
If not, don't just cop a feel or groom people to put up with your touch. You have no idea what people have been through. You could needlessly offend or retraumatize someone.
If you are in an uncertain situation but still think any of that potential hurt or those consequences are worth a sexual thrill just for yourself, then you really are a creep.
Grabbing a breast, or someone's ass, or grabbing their genitals, YES, of course those are culturally forbidden areas that are illegal to touch. "Copping a feel," if you will. Yes, that's sexual assault. I have never done anything close to that in my life and would punch someone in the face if they did that to my daughter or any female I care about. Less bad, but still wrong, would be stroking someone's hair, or smelling it, or rubbing their shoulders without them asking. To suggest tickling someone's exposed FEET in a playful situation is in the same category of that is preposterous. And no, it doesn't matter if we find it sexual, that's completely irrelevant.
You are failing to consider the fact that some people have been sexually molested in childhood and tickling is usually a big part of that. Or someone might have been held down and tickle tortured by their abusive brothers past when they demanded the tickling stop and thus HATE it and get a PTSS-esque response. But if you really want to say that being respectful of other people and not touching them without invitation is "finger wagging" at you then go off I guess. I hope the people in your life find this account and realize you've been tickling them for yeaaaaars of and on. Wonder what they'd think of you tickling them knowing you got your rocks off to it later?
I'd say the same thing to you, Hec: lighten the hell up. You're jumping right to "sexual molestation" and these absolute worst case scenarios of torturous non-consensual sibling tickling and PTSD, and I'm talking about tickling your friends foot you see hanging off a couch for 5 seconds for fucks's sake.
As I said in my original post, the tone of what you're saying, the atmosphere, the relationship, that's all relevant. But the fact that the tickler finds it arousing (Sorry, Wolf) is 100% not. Take hugging: Some people are extremely touchy about being hugged and hate it. If you know that after hugging them once, and you insist on strongly hugging them every time you see them, you're a bad person and a bad friend. To Wolf's point, whether YOU get your rocks off on the hug later is completely beside the point -- you're doing something you know your friend viscerally hates. That's the wrong. Not the fact that you were turned on by it in your brain. Again, that itself is nobody's business, and to think it is is narcissistic. It's not your business what goes on in some else's mind, and vice versa.
And if I found out a gay friend of mine jerked off in his bedroom after hugging me every time he saw me every year or so (I don't love hugging, but I don't mind it) what the hell business is that of mine?
Non-sexual, innocent immediate tickling makes people laugh, it can the lighten the mood, it can connect people. I speak from experience. And I again state I have zero guilt or regrets for any innocent tickling I have ever done. There are lines all good people know you don't cross, and I never have.
Remember: While WE may find even innocent tickling arousing, 99.9% of the rest of humanity does not.
Tickle away, people!