I don't know much about the Political Defiance approach you linked. Could you summarize it (the link is a whole book).
Overall, I agree with you. I don't like violence, and I think it's one of the least effective tools for constructive change. But I also recognize that if you're serious and honest about political theory you can't really just write off violence as "never the answer".
At the very least, folks need to think about approaches to defense when people with less compunction about violence come for them.
Also, I want to add that my personal theory is that combatting fascism requires a lot of separate approaches and distinct actors working in a way that is synergistic, even if people within that effort have strong ideological divisions.
My personal role is that I'm focused on efforts to demonstrate and promote the alternatives to fascism -- socialism -- locally through politics, labor and tenant organizing, and mutual aid. So I'm not picking up any guns any time soon. But I'm not going to tell the black bloc folks how to do their job and I expect they won't tell me how to do mine.