I don't see how they can bring a red flag against you if you end up with tainted coins. lets say they have been passed about for a number of years the taint will always be with them, Just look at some of the coins from the silkroad and places like MTgox hacks..

Those coins are still rolling round out there somewhere, But dose that mean if you by some "legit" reason you ended up with some of these coins places like exchanges would refuse to accept them?? Or worse freeze them?

https://blockchain.info/taint/1GmPZeLn93CJnu8r4hdeFfRtQyF3mXNRQy

Here is one address that was used in movement of Gox funds.. The taint analysis says it all