Well there's two parts to it, firstly yes, it's morally wrong for him to have an affair. I'm not sure if that particular part of it would warrant being fired. The part that I think is particularly bad is who he was having an affair with.

I'm kind of bemused by this "But Epstein" defence. No one thinks that's a good thing! Seriously, is that how we run society, if we can point to any grievous failure of justice we just suspend all further rules? No. Of course not.