There is real life tickling that approaches that all the time even outside fetishism. If you consider the sibling dynamic and the dastardly evil some can be tempted by in youth, it happens. Whether it's holding someone down or whatnot. The question is context and the nature of somebody. Is it a significant other and it turns the both of you on? Is it it a sibling and you're pushing the limit some knowing what they can and can't handle? Is it very random and especially vicious with someone you don't know? How long are you pushing it? There's a lot of factors and I don't really think it has to be "sick and perverted" at a base level unless it's a kidnapping or you're going way, way WAYYY overboard with someone who you don't have a read on.
It's definitely a lot safer in fiction or a production. I won't lie and say that I don't get turned on by fantasies involving that or even supposedly true accounts that vicariously get to me. Generally I prefer consent and/or pre-arranged understanding. At least to the level of BDSM play where limits are pushed, but you're asking for it. Regular, "real life" tickling can go a little overboard without being horrifing, but if you're talking 2 hour marathons by a burglar or villain and the victim is destroyed, nah. That doesn't happen on the regular without serious consequence.
