They are taking the risk of getting questioned by the police and possibly doing time. That's the risk they are taking for buying these tainted coins.
Say that I received 1 BTC from ISIS. I send this bitcoin to whirlpool. It's getting mixed 'til eternity. Please explain me the risk from selling coinjoined coins. I have no direct relation with ISIS from a blockchain perspective, and chain analysis will simply flag it as "taint" because of its inability to track it, just as with XMR.You brought decentralized solutions to the discussion but last time I checked, bisq was a ghost town and exchanges like eXch aren't really decentralized.
I love how we transitioned from "certain coins can be traded for a 50% discount" to "b-b-but Bisq lacks liquidity". You know what it brings to mind? "Bitcoin holds no value because no vendors accept it". 
If there's insufficient liquidity, make an offer. As for eXch being centralized, yes, it can be shut down. But, is it currently treating all coins equally? Yes. Are there more swap services that stick with the same notion? Yes.
Every other single person out there who's using dex's and how many are there of those people actually? Can you give me a number? And compare it to the people that use centralized exchanges maybe? What is the rate? 1 to 100? 1 to 1000? 1 to 10.000? There aren't as many people that use dex's. as you think there are.
"How many people out there use Bitcoin as currency, 1 to 100, 1 to 1.000, 1 to 10.000? It's not money!" 
As for Andreas, I don't completely agree with him on this matter. He once told its viewers to send coinjoined coins to themselves for k times so that "taint" can disappear and their centralized exchange accept their private coins, which is completely moronic, and due to the nature of "taint", is not guaranteed to work.