Even without a mixing service, there is no way to prevent somebody from sending you tainted coins.
Yes, this is also an important point.
Just picture the following scenario:
Hey, I want to pay you
No way, your coins are related to the recent hack!
I already sent them to your address. U MAD BRO?
It might be ridiculous, but it's totally possible. What will you do then, now that you yourself are tainted too?
WoW, nice. I mean evil.
Just send a few coins to some reputable exchanges/services and done.
Pure evil.