Sure it sounds harsh from a strictly academic point of view, but you may think differently if some drug dealer was trying to get your kids hooked on crack or heroin.
I wouldn't use only "how effective it is" as a guideline here - there is also the issue of morality, and what other solutions might exist, that aren't being pursued. Personally, I don't think there is any justification for using the death penalty; not only in this case, but in just about any case I can think of.
Of course, as (oYo) points out, it's easy to have this view if you have no personal connection to the victims; but as harsh as it might be, in my view, that should have no bearing on the situation.
Indeed, the first line of defense against drug abuse is love and education.
But, (hypothetically speaking) what if someone literally put a gun to your kid's head and made them do it with the intention of getting them addicted? (I know this sounds extreme, but it's not really that far off from what really does go on.) This degenerate is basically trying to destroy your child's life and in my eyes deserves no less than the destruction of theirs in return. It has nothing to do with being a deterrent, but more to do with ridding society of such professional scumbags. The sorry truth is that these people aren't likely to be rehabilitated and will only become worse and more dangerous over time. And, if so, why should good people be saddled with the burden of supporting the life of these people in prisons, where they hone their skills? I feel the same way towards pimps and rapists. I have more respect for the life of a