Nerd, as it is used, appears as a combination of machism (lack of) and anti-intellectualism. The ableism takes a back sit, but it is still there, I've been called nerd for not liking certain social environments.

The neckbeard is a sancocho of shutin stereotypes of unaccepted social behaviors, like poor hygiene, innapropriate topics of conversations, blatant sexism, serious objetification of women, obssesion with niche activities (like videogames or anime) and a lack of self awareness. In-group, they justify these behaviors on their autism (which I find to be copout^?, because it doesn't prevent them from not being an annoying asshole) or the world around them (which in the rants I've read, their complaints seem more like xtreme reactions to minor slights).