They have ratings systems on there to help this - obviously it doesn't mean it's not possible to get stuff that isn't want you think it is, but it's not too much better or worse than trusting a local dealer on the street.
If you kill people slowly, so, booze, fags, fatty food, pollution, and so on, then its fine. Killing people really fast, well, that's then it gets iffy. Oh, unless you are a government waging a jihad, or is it "war", on something.