The reality is that being “anti-Nazi” is also a neutral stand. This is in the terms of service of Proton:

Unauthorized activities include, but are not limited to:

[…] 4. Harassing, abusing, insulting, harming, defaming, slandering, disparaging, intimidating or discriminating against someone based on gender, sexual orientation, religion, ethnicity, race, age, nationality or disability;

I don’t think Proton is ok with Nazis, but I feel people wanted them to be also “anti-Trump”, even if Trump does something to benefit privacy (which, as you hinted, is a neutral action that also benefits anti-Nazis).