It's because those people have an agenda they want to push and everybody who goes against them must be neutralized and the easiest way to do that is to slap the far-right label on people.
It's why they hate Trump so much, this guy actually explains it well:
This is why they are attacking incels, not because the existence of lonely virgins offends them, but because incel theories about women and reality, the blackpill itself, are a treat to the globalist religion. All those IT people who attack this forum constantly? They are all doing it because they cannot suffer the existence of people who don't think like them because the hegemony of their world view relies on total domination and the absence of all dissent. They already control the thoughts of normies completely, but there's always those who escape the Matrix one way or another, and like i said the easiest way to deal with the existence of dissenting voices is to use the Nazi card. This is why it's actually a waste of time to point out to them that many incels are neither political nor are they even white. They already know that, but they don't care because to refer to incels are right-wing and white is their way to shut incels up.