I think it varies a lot, mostly on the person's background and own personal experiences. A lot of people don't usually discuss sexuality in any form, so the mention may be a bit awkward, and you may very well get a strange response from them.
I think a lot of younger people are starting to grow up with several influences from the internet, so we're all kind of waking up to just the awesome number of fetishes and sexual interests there are in the world. And when you throw all of them in a bowl and compare/contrast each one, I thank the gods that I'm a tickler...every time.
So in that vein, I've yet to find anyone in the real world that looked down on me because of tickling or what have you. I think many "vanilla" people tend to think of it as very kinky and sexy, but just don't take it as far as we do. Maybe I've just been lucky enough to be surrounded by relatively open minded folks.