No one is saying dont fight nazis. We're saying dont do nazi-things and justify it by saying im fighting nazis.
Because when you beat them, you're going to take your new nazi-powers and ideals and use them against non-nazi's. It's only ever worked that way and you convincing yourself youre the exception is the first step.
What "new nazi-powers" do you believe were asserted here?
Do you believe this is the first time that anyone has taken down a website through hacktivism, or that "the nazis" have never done anything of the sort?
What "not nazi-things" specifically do you suggest would be effective for fighting nazis?
You'll probably say "simply debate them on the merits" but that doesn't work.
And it's odd how in this argument the slippery slope is only ever a danger when people fight nazis, and never when people allow nazis to gain power and proliferate.