If a society is experiencing serious social problems, millions of people can vote for far-right, fascists or ultra-nationalists. It happens for the reason that ultra-nationalist forces offer simple social solutions: to take away property (money, benefits) from the "wrong" part of the population and transfer to another "good part". Chicago sociologist George Derlugian notes that many people easily agree to such conditions, because this decision seems to them very simple and convenient.
Anti-fascism is trying to argue from the standpoint of the protection of tolerance and so it can not solve this problem. The truth is that so many people do not need tolerance, they just want to improve their social situation. These people may be enough to bring the Nazis to power.
It's not like "anti-fascism is just a tactic." This tactic does not work: historically it failed in Germany and Spain in the 1930s. Anti-Fascism is focused on the fight against its political opponent, has nothing to offer millions of disadvantaged people who are not interested in the idea of tolerance. Anti-fascism does not provide alternative motivation for them to fight.
When the state in Spanish Republic put the economy under its control and forced people to work in poverty and hunger, their motivation to fight fascists fell sharply in 1938 - 1939. Italian anarchist Camillo Bernery warned that the population suffering from poverty would not identify themselves with the anti-fascist Republic. After the fall of Catalonia in February 1939, members of the CNT National Committee (anarchists) admitted that the population "no longer feels the enthusiasm of the first days" [of the revolution] (Vadim Damier. The Forgotten International. p. 404).
Anti-fascism can be successful only if its opponent is another street youth subculture. Maybe one mob can beat another in a street fight if it's better organized. However, if fascism turns into a mass public mood, then anti-fascism will inevitably be defeated.
Historically, millions of workers of different nationalities can only come together if you offer them an alternative collective way to change lives: Autonomous multinational workers сouncils that fight together to improve the situation of all workers (and then one day take control of production and infrastructure). https://libcom.org/forums/theory/it-somewhat-gives-me-vision-what-ongoing-anarchist-communist-society-would-look-16
The Addition A: The campaign "against ideas of hate" is not a practice of self-defense that the masses can use. This is idea of the rich tolerant liberals. Calling the people to say "No to sexism, homophobia, racism!" is a waste of time, it's a meaningless bourgeois ideology. Who are you talking to, the poor Afro-Brazilians who will fight against the Nazis? Are you serious? Masses of poor people will be able to defend themselfs only attacking fascists and bosses. Of course, we can say: "This is not driven by hatred, but by the purest love of all mankind. And precisely because of this love, we have hatred of those who slaughter us and preach hatred among us, so we are for war against the rulers". But anyway the main weapons of the masses is a hate-speech, not tolerance.