OMG, can't believe we're on page three for such a reta... "obviously unnecessary" question.
I really don't get it, OP: You were gonna forbid a totally harmless usage of a certain spell, because you could think of a totally broken usage of the same spell along the lines of a (wrongly assumed) analogy in the logic of said harmless usage? Wow.
I mean, it isn't as if you couldn't have allowed the spell to desalinate sea water and STILL rule you couldn't no-save-kill somebody with it... man, I feel dumber just spelling that out...