Well, the alt-right from what I remember from a conservative friend who watched it for a bit did say that it is pretty loose group like SJWs (in my experience).
Like the one thing that they had in common was disliking the popular/mainstream conservatives due to seeing them as incompetent, not conservative enough, or corrupt.
Aside from that, there isn't much other than their opponents and the established conservatives who they want to replace that unites them really. Again, actually like SJWs since even tvtropes noted how Tumblr in their YMMV page has this:
"Within the social justice circle, there will be a fight between bloggers who lean more towards a certain issue. It's not uncommon to see black SJWs fight with gay SJWs over homophobia in rap, or black SJWs proclaim that Asian pop steals from black culture and angering Asian SJWs in return, and black SJWs fighting amongst each other about how offensive the newest black comedian is, et cetera, et cetera. Even within the LGBTQ circle of bloggers, there are debates over whether or not cis members of the community should have as much as a voice due to the issue of trans* erasure, and you'll see radical feminists fight with transgendered bloggers, with the radical feminists accusing transgendered people of crudely pretending to be female or abandoning their femininity. Feminism, in general, tends to be a minefield, as well, when bloggers aren't being harassed by angry MRAs and trolls.
WOC feminists versus white feminists, though the hate is usually one-sided. WOC feminists hate white feminists for considering themselves separate from white male oppressors, citing racist feminists during the first wave of the feminism movement, while white feminists ally with POCs more than white people on issues of race, considering intersectionality to be important."
Both from what I can tell are pretty much reactions to the world not being perfect, not getting better or ideal in their eyes. Thus taking matters into their own hands, even if it means fighting with people that are technically on their side but due to differing priorities, beliefs, values, measures and relationships will inevitably fight since in some of their eyes