Regarding your question, I think some people would accept them, but they would probably ask for a discount (maybe up to 50%). Paying 0.5 BTC for 1 "tainted" BTC would seem like a good deal. As always, it's the free market that dictates what should be done.
Some would even exchange it for XMR afterwards, temporarily at least.
Yes I have heard about deals like that before.
So are you telling me, it wouldn’t make any difference to you if I wanted to sell you some coins with very bad history? (Maybe Isis used my coins to fund their operations or I got my coins from an exchange hack and I am that hacker) I want to sell you my coins directly, without using any third party exchange/mixer. Would you take this deal?.
Yep. No problem.
Amazing.

BTW, do you know your coins' history? You do know that ISIS coins might be sitting on your wallet right now, right?
Might be. I am getting my coins from an exchange and sig camp payments. I don't have any other coin income. So If my sig camp payments are tainted, It might cause me problems. I heard binance locking people's accounts randomly without a reason and these people did their KYC already. That might be the reason why they do that.
Would he take that deal?
What kind of question is that? Is it fungibility or morals the topic?
Fungi.
Let's see what fungibility means again.
being something (such as money or a commodity) of such a nature that one part or quantity may be replaced by another equal part or quantity in paying a debt or settling an account
"One part or quantity may be replaced by another equal part or quantity"
So, when cryptosize above said, people can take them bad coins for a discount, it already violated the description of fungibility. And when nobody wants these tainted coins, that means these coins can't act as currency anymore. If nobody wants them, they ain't fungible. (except for you, to you they are still fungible. The FBI will buy that story I think, good luck

)