The demonization of incels comes from feminists to a large degree, but I also think men are often highly motivated to do the same. Not just in their typical gynocentric support for women's interests no matter what, but also as an act of self-preservation. Two things. Competitive advantage in the mating game suggests men will want to increase the pool of losers and the more men can be cast out of the game as incels the better one's chances are. This is quite literally how extreme Mormon sects like in Bountiful, BC. structure their communities. The 'incel' men, the losers, are forced to leave so that the others can have their choice of multiple wives.

Following on that, the dire stigma of being thought or labeled 'incel' is an incentive to disabuse anyone of the idea by using the label oneself, preemptively. At this point, the term has become a slur or a smear so that men are falsely being called incels when they are not, for such crimes as pushing back against feminist ideology, or caring at all about men's rights, or just willy nilly.

So I think we not only have to examine the feminist narrative, but also more fundamental biological drivers that serve to further marginalize an already vulnerable group.