If $0.0001 in tainted funds can taint a wallet containing a billion dollars then everything will end up tainted immediately, whether a result of trolls or just funds being transferred by ordinary users in jurisdictions that don't enforce the same sanctions. But if nothing is tainted because everything is then the sanctions are meaningless because someone with sanctioned funds would just deposit them at a major exchange in a foreign jurisdiction and then withdraw them again as untainted funds.
Well one of the problems here was the sanctioning of a technology, which AFAIK has never happened previously.
Exchanges have the means to work with regulators, demonstrate good faith, and get themselves removed from any accidental sanctioning. This doesn't exactly apply to small tips akin to BuyMeACoffee.