I don't eat meat either, but I still don't see why murdering murderers is wrong. If somebody stole something from you, you'd steal it back wouldn't you? But that second act of stealing isn't a "second wrong", it is a corrective measure. Murderers need to be treated differently from non-murderers, and frankly I think instant death is more humane (not to mention much less of a burden on society) than sticking them inside a dingy prison for the rest of their lives.

Some people just plain don't deserve to live. For instance, if Hitler had been captured alive, would you suggest life imprisonment or some similar punishment? Me, I think he should have been subjected to a long, painful, torturous death for his crimes.