It's more that we have so much evidence, from actual FOI releases, state-dept employed/funded papers about actual brainwashing, and plots that went wrong and got exposed that it's rational to be extremely sceptical.
It's not even that the default assumption/threshold of proof thing has inverted, it's that it's reasonable not to assign it to your heuristic interpretation of trends in how people actually think--and again we have a lot of reason to understand that there's a deliberate drive for media to push that just kind of tribal faggot thinking--there's just too much noise in the system for that.
So when people make apparently absolute statements about glowshit they're really just expressing that and inviting others to ask the same question first.
You can't expect to have entire government bureaus making an industry out of radicalising retarded kids for decades without it eventually having accumulating secondary effects go rampant. Both in terms of the mechanisms they use eventually gaining a life of their own, and rightly or wrongly how people are able to interpret motives whether someone is an actual target, secondary loons, or genuine free agents. And in turn we gotta factor that uncertainty into our thinking at a certain point. Which we're way the fuck past.