"Why not"

Thanks to Michael P. for the link to Adam Liptak's piece on the death penalty and deterrence.  I don't think he will disagree with my view that the fact that X "saves lives" (as, I am willing to assume, just for the sake of argument, the application of the death penalty does, in some sense) does not tell us whether or not X is morally permissible (even if it is a factor that might, with respect to some acts and contexts, weigh in X's favor).  This is one reason why, in my view, the (so-far-unsubstantiated) claims that, say, embryo-destroying research will, somehow, improve the health of ill and disabled people do not provide particularly powerful support for the assertion that it is morally permissible to engage in such research.