Could you clarify what exactly is a "user registered in Russia" that you are banning? I left the country (because of the government), and now have american billing info in my account, but I still got the termination email.
They also have what sounds like a sizeable workforce in Ukraine itself, so it should be pretty obvious why they chose to blacklist the entire nation invading their direct coworkers'.
Some US citizens with Russian heritage could have Russian addresses listed like 10 years ago.
Would be funny to see this case in court.
It's just like how Walmart.com doesn't ship to China. That's legal. And if I'm in the US, and I put a Chinese address on my Walmart.com account, and they don't ship me a package, that's not discrimination, that's just a mistake.
Now, if Namecheap starts intentionally going after people of Russian origin outside of Russia, that's a different story, but it doesn't look like that's what's happening here.
There are a few words for that philosophy, and legality of that business practice becomes questionable.