Personally I've tickled a girl who's a close friend who doesn't enjoy being tickled because she's too ticklish, if I just give her a quick tickle on the ribs or something playful then she doesn't mind at all. Thing is, I'm not going to say to her "will you give me consent to tickle you so that you can't sue me for sexual harrasment?" She's a friend and she doesn't mind it, just like with noogies, it's annoying but it's a playful annoyance. She trusts me not to go too far and I respect her enough not to go too far.
I personally thought compairing it to rape was a bit of a stretch, but that's my opinion and you are quite in the right to disagree. Maybe I'm just seeing the whole thing in a different, innocent light. I could be completley wrong.