I didn't say acceptable, I said "not illegal". To me, it's just dirty tricks.
In my OPINION, the House Comer committee generated stuff about the "Biden crime family" much of which was ... not convincing, to me. It was a made for TV exercise never meant to impeach Joe. Entirely legal. It happens, often.
If someone has illegal income from "China", the easiest way to catch them is on tax evasion, or it can be proven if they reported said income. If Joe got illegal income, his returns are public.