I guess it depends how bad you want the item. Ideally, I’d like to say just cut the loss and don’t support scum bags.
But then, I know that if someone had the last two cards I need for an unreleased set that I don’t publicize because I’m afraid someone else will finish the set and rob the market of the cards I’ve spent years of my life hunting for, i would probably buy them from ISIS if they had them.
So i guess only buy it if you have absolutely no other way of hoping to obtain the card. Otherwise, reject it on principle.