All fetishes have creeps. There are always people who don't understand and act inappropriately, especially when the situation has a sexual element.
However, I think the reason why the tickling fetish seems to have a strange problem with creeps is because of the nature of the fetish. It's tickling. It's something that most people have experienced in their lives on some level. Most children were tickled by their parents or their friends and have probably tickled them back. To an extent it's normal human behaviour. Unlike something like hardcore bondage, where the only people who have any experience with that are the ones who have actually actively sought it out to have a sexual experience, most normal people do have a frame of reference for being tickled. They know what it is and understand how it feels and so the thought that it might be someone's fetish is weird to them because they actually have experienced it and it very much wasn't a sexual experience for them. The fact that they were probably tickled as a child and therefore may associate it with kids also doesn't help.
The other problem is that because it is seemingly innocent to many, the creeps think they can get away pushing harder with tickling than they could with hardcore bondage or something more extreme. It would be kind of hard to 'trick' someone into answering a question about hardcore bondage (or especially engage with it further) without them realising why the question is being asked. The question "Are you ticklish?" sounds far more innocent and less threatening then "Are you a 'Spread-eagle' or 'inverted Y' kind of girl?" despite the fact that both may be unsolicited attempts to get an answer for their own gratification. Now bondage creeps probably know that if they asked that second question they wouldn't get an answer while a creep from this community knows that they can possibly get the answer they want if they ask it in the right way.
Unfortunately, I don't see this going away any time soon. Even if we could convince everyone on the forum not to do this there are plenty who have the fetish and don't engage here. Part of the thing is that even now, the tickling fetish isn't very widely known. As such, while creeps do occasionally get called out, they're still able to get away with it a lot of the time. While a couple of the people who have been asked on Cameo have called out the question and others have refused to answer, there are still literally hundreds of celebrities who saw that question and didn't associate anything sexual or creepy with the question. Even before cameo really took off I remember once seeing a celebrity respond to the question on twitter by talking about how ticklish they were. And it's not just through Twitter, it can be TV productions as well. A couple of years ago the Australian TV show Neighbours decided to release some promotional interviews for their new season where people wrote in to ask different cast members questions. I think it was kind of a 'get to know the cast behind the scenes' kind of deal. Hundreds of questions went in from fans and they were all carefully vetted by the staff to remove anything controversial or inappropriate and yet somehow one of the questions that got through and was chosen for airtime was asking one of the actresses whether or not she was ticklish.
To be clear I am not saying that I want the fetish to be considered creepy or weird, or even get any more attention than it already has in the public consciousness. I'm just saying that the nature of the fetish means that it's not as immediately threatening as others can be and therefore it allows creeps, who are usually kind of sneaky people by nature, to push their luck further because it's less likely that someone will catch on to what they're doing as quickly. That's what I think anyway.