While I don't doubt some ticklish people have zero tolerance for getting tickled no matter who tickles them, 99% percent of those who tell you, "I hate being tickled," are actually saying, "I hate having you tickle me." It almost always depends on who is doing the tickling.
I can hate it.
Just because you have a tickling fetish doesn't necessarily mean you are good at tickling.
Just sayin'.
I hate it if it happens anywhere in the vicinity of my family. I also hate it when i'm trying to do something important and someone just decides; "Ah look there, he's tying to disable a bomb, tying to figure out which wire to cut. Seems frustrating. You know what would be an amazing idea!? Tickle him!" *BANG!*
Okay, that's kinda overexaggerating! But only little.