There are a lot of people on the politics threads who are good at debating and questioning a point and request evidence/backup of statement made.
Moreover, on the wider Internet there isn’t. I’ve seen this happen on remain FB groups even (though far, far less often than leave ones), there’s plenty of folk susceptible to Fake News on both sides of the coin. People are generally very quick to believe something that reinforces their existing views (which, of course, is how we got to this point).
As you say though, STW on the other hand has a healthy collection of mass debaters well practised in going “prove it” any time someone dares to try and claim that grass is green. With a handful of notable exceptions, most of the leavers have scuttled off now as their arguments have been challenged and demonstrated to be baseless. This challenging isn’t really happening effectively elsewhere, people are just getting angry and abusive at each other, which of course will earn you time off on here.
And if you remove people’s ability to be shouty, what else have they got left? Either change the subject, come out with some bollocks like “what part of leave don’t you understand?” or scuttle back under their rock to be jingoistic in private.