Bitcoin is not fungible because the full transaction history of every single bitcoin is available publicly. This means you can discriminate against specific coins because they were at some point involved in undesirable activity. Exchanges already reject these tainted coins. Even using a mixing service for privacy's sake is enough to taint them.
On the other hand, we have fungible coins such as Monero. It's impossible to tell where the coins are coming from so there's no way to discriminate based on the source of the coin. Their only option is to stop trading XMR as a whole.
On the Monero blockchain it's not even possible to find people's wallet addresses. Interestingly, on the US treasury sanctions list a transaction hash appears as if it was an address:
https://www.treasury.gov/ofac/downloads/sdnlist.txt
> Digital Currency Address - XMR 5be5543ff73456ab9f2d207887e2af87322c651ea1a873c5b25b7ffae456c320;
Note the lack of the 0x prefix. Here's the transaction on the block explorer:
https://localmonero.co/blocks/search/5be5543ff73456ab9f2d207...
Basically tainting with FIFO.
Monero hides the sender, receiver and the transaction amount from the public.
While it's not a perfect system (ring signatures being the main weakness), it's extremely difficult to trace and you can for instance sell them on Kraken directly for cash.
(Incidentally also, there is a minimum unit, at least in all currencies that I know of; Bitcoin, for example, goes to eight decimal places. But yeah, each unit doesn’t have physical identity like bank notes do. Infinite divisibility is bad for efficiency as it means your data types have unbounded memory usage, so you’d need to put together a bunch of rules about how far you actually can divide things, and it’s just not worth it.)
Yeah I think this break your hypothesis.
Every single major account will just end up poisoned. Easily done by finding the addresses with most coins and sending them fractions of coins from tainted account. Tesla will be the first.