Not disagreeing a good number of these particular issues are marginal, and that politicized narcissism plays a prominent role in much of this. But what's also true is that this whole development is - in the grand scheme of things - mostly marginal, too. The stuff you mention is mainly a matter of serious concern in social microcosmoses like certain university campuses, or in the alternative reality of twitter and sensationalist internet news. That sure doesn't mean it's irrelevant. But perspective matters, and that's what often goes missing in the excitement about things like that.
If you look at a more representative social environment, say, a public school, you are usually not dealing with kids terrorizing others over halloween costumes or micro-aggressions. Teachers will have more trouble stopping some of them from calling others a faggot, a whore, a [racist slur of choice], or bullying/beating up the outsider kid for 'looking stupid'. It's still the classic stuff that's by far the biggest threat to individual freedom from discrimination and violence. And this is true for the adult world too. Denying this simple fact, and trying to stop or dismantle vital counter-measures is, by and large, at the heart of today's anti-pc project. Everyone criticising things like the ones you mention while having more noble goals has to take that into account.
In the end, the tedious outrage rituals of anti-pc crowds work in the same way as those tedious outrage rituals they preferably attack: hyperventilation over, essentially, minor points. And I'd go as far as saying that for the majority of its proponents this is a deliberate (while not always conscious) strategy. They build up 'pc oppression' as a strawman in order to reassert the partly lost cultural and political dominance over minorities. They are also much more numerous and, as a group, dangerous than their activist counterpart.
I'm all for criticizing twitter infantilism and pomo-authoritarianism. But everyone doing so needs a clear idea how to avoid ending up in the same boat as people with Pepe avatars. And when (for example) looking at this thread, this effort is too often lacking.