The only way one could know he is playing russian is when the person deliberately choose to present russian flag. And by doing this they automatically show a support to russia and its actions.
There are alternatives: not to show flag at all, or there is an "alternative" russian flag - but some people willingly choose a symbol of aggression. No wonder not everyone feels ok to play such people pretending that nothing is happening. As mentioned in #3 FIDE did ban russian flag, but lichess did not, so users are kinda forced to play war supporters or get sanctioned otherwise.
There are alternatives: not to show flag at all, or there is an "alternative" russian flag - but some people willingly choose a symbol of aggression. No wonder not everyone feels ok to play such people pretending that nothing is happening. As mentioned in #3 FIDE did ban russian flag, but lichess did not, so users are kinda forced to play war supporters or get sanctioned otherwise.