I would.

It's not Protonmail who's to be blamed for the potential attack and deaths. There are series of events that lead to people deciding to be terrorists. I'd focus on those reasons rather than hotfixing stuff by exposing 99.9% of other Protonmail users.

I would never opt in to affect 99.9% of users because of 0.01% of users. We are all educated enough through events in recent history that clearly tell us how similar use cases lead to abuse, every single time without exception.

Given these constraints, Russia's decision to block Protonmail is perfectly fine and the only logical outcome.