"Taint" doesn't exist in the blockchain, (...)
But in the laws (of various countrys).
If a 8 year old is producing a block in the BTC network, it is illegal in Germany. If a drug dealer is selling drugs for BTC, it is illegal in the USA. And the authorities of these countrys are tagging the coins and adresses. This is the fact. Basically if one country is defining BTC as a good, the good can be stolen. And the receiving and/or buying of this stolen good is/can be illegal.
The BTC network cared for these illegal activities. But most of the answers were: It is a small problem in relation to the benefits. But the answer is not solving the problem. The same problem is existing with FIAT. But partly solutions are restrictions of the trading amounts, KYC and tax investigations/trackings. And of course physical markings with special colours or tracked bill numbers.
Basically every Satoshi could pegged (by the BTC network) to a NFT. And if one country is blacklisting it - because of the law - it would not be tradeable in this country. So in the end the price of this one Satoshi would become less value as another Satoshi.