Pidor (пидор) is a Russian/Ukrainian/Belorussian obscene short for paederast. Very often used not in sexual orientation meaning, but as a swear for disgusting, dishonest and slippery man. It is nearly impossible to spend some time with military and do not become familiar with Rusiian/Ukrainian/Belorussian swear words. They use them constantly and you just will not be able to communicate with your military pals during doing something together without understanding obscene lexicon. They literally talk on that slang. Completely meaningful phrase could contain only obscene words and few prepositions. Something like "пиздуй туда и прихуячь вон ту хуйню на вот эту поебень, чтобы не пиздануло" - "go there and mount that thing on this device to avoid problems". And it is even not offensive at all, just regular workflow thing.

And did that pidor really find himself on Ukrainian side?

However, it could be just a rare now anti-narrative reddit troll.