True. But without knowing all the details we can't make an informed judgement. Do husbands cheat on their wives after they found out that their wives cheated on them? It's possible. But we don't know.Anyone that will cheat on their spouse, will cheat anyone.
I agree with the OP that judgement calls should be evenly distributed across the political aisle. I doubt that Platner's infidelities are nearly as egregious as Trump's (think Epstein Files).