that taint might be used to block legitimate owners of bitcoins from spending the bitcoins?
people who paid for or mined bitcoins, not able to spend the bitcoins, and accused of being thiefs?
Yes.
Cars might be used to run over innocent living humans, or pets even. Shall we stop driving?
Big difference, however: Only one driver is required to use a car for bad purposes. In order to really block tainted bitcoin from being spent, ALL the miners (including the person trying to spend the coin) would have to block it. The stop-thieves-using-taint strategy only works when a significant portion of the miners (or folks who accept bitcoin) decide to employ it.
I'm going to keep driving, because I drive safely. And I'm going to keep an eye out for bitcoin from the known heists, but I won't do much about it without doing some due diligence first. You're welcome to be sloppy with it - the bitcoin, that is, because your errors will likely be quickly corrected. But with your car, please drive safely!