Casting Too Wide a Net
There has been a net cast too wide towards groups of people assumed to be "extremist" or "far-right" or "hateful"
There are groups of people who contain some people that could be described in this manner, but cannot be remotely uniformly characterized this way.
Anti-SJWs-All it takes to be an anti-SJW is to reject left-wing identity politics, and there's a spectrum of people who disagree with left-wing identity politics for different fundamental reasons. There are right-wing identitarians who reject left-wing identity politics because it is opposite of their own identitarian views (be it the alt-right and their white supremacist white nationalist views, legitimate actual sexists who hate women or think they're inferior, etc.). But there are also in greater numbers the individualists such as myself who reject identity politics and identitarianism across the board on the principle that people should be accorded rights and judged as individuals on the basis of their own individual merits and character. There are also types of marxists who would fall into this category funny enough, because they believe identity politics is a distraction from class politics (marxists are actually extremists though, just not the type being discussed in this thread)
Antitheists-Again ****ing weird that I'd be the one to defend antitheists, but they merely believe religious thinking is dangerous to society because of their fundamental ideological disagreement and criticism of religious thinking. This doesn't make them people who inherently hate religious people, or want to persecute them, or kill them, or genocide them, anymore than a left-winger who finds right-wing thinking dangerous and disagreeable wants to persecute kill or genocide right-wingers. The Sam Harris/Richard Dawkins/Patientleech types are not extremists. There are some antitheists who are extreme, the kinds who throw around statements like "religious people shouldn't be allowed to run for office" or "religious people shouldn't be allowed to vote" or "religious people shouldn't be allowed into scientific fields" or "religious people should be sent to reeducation facilities" or "religious people should be killed," but these types are few and far between.
People critical of immigration-Being critical of mass immigration or illegal immigration isn't an exclusively alt-right/ethnostate/genocidal position. You could be someone legitimately concerned with... I don't know... the indiscriminate mass migration of people from nations where women are treated as second class citizens and gays are heavily persecuted. It isn't racist or ethnostatey to be concerned with this. You can be against this mass immigration policy and still not believe these people should be the victims of hatred violence or mass murder (because tightening borders is not genocidal), or even not necessarily entirely against immigration (you could want it at a slower rate with proper background checks so that you could welcome people into your country at a rate at which they could culturally assimilate). You can be against illegal immigration in the US because you want the border laws to actually be enforced, and because you want people who immigrate to actually go through the proper legal procedure to do so. You could be against immigration because you're an economic protectionist who wants to protect the jobs of the people who already live in your country from increased competition and wage depression. Then of course there are the people who are against immigration specifically because they do want an ethnostate.
Men's Rights Activists-There are some men in these groups who are bitter sexists who hate women. However there are also some men (and women like Karen Straughan) who have legitimate grievances or concerns, such as the draft, or boys falling behind in the education system, or men losing custody of their kids more often than not, or being unfairly assumed to be the perpetrators in domestic assault cases, etc.
Nationalists-There are some people who are nationalists because they are fascists or ethnonationalists, this is true. There are also some people who are nationalists or nationalist-leaning who come from the point of principle that a national government should first and foremost consider the interests of its own citizens who grew up there, have paid its taxes, and have been subject to its laws for years, such as people who are economically protectionist who think their nation in its trade or immigration policy should favor the jobs of its own citizens. There are also those who would like the law of the land to be closer to the control of the people who live under it, such as the people who are euroskeptic and would prefer that their laws be made by their own elected national representatives rather than have them be decided for them by bureaucrats and citizens from other countries.
Pewdiepie Subscribers-I... I can't believe I have to say this... but no, ****ing Pewdiepie isn't alt-right and he isn't radicalizing people to the alt-right.
Meme trolls-Meme trolls just exist to troll people honestly, generally to troll the left. The population of people who would enjoy triggering the left with memes does include the far right, but it also just includes anyone ideologically opposed to the left-wing who wants to have a bit of fun with it.