Kittens, effigies, or governments, I find the language distasteful and reprehensible.
In my own languaging, I might say, "let's take this out and kill it". If I'm being casually colloquial, it's possible that I might say "that needs to be shot in the head". I can point to first person shooters for desensitizing the imagery of the last statement to the degree that it's used colloquially, much like the imagery of rape.
I'm having difficulty parsing "drown it in a bathtub" back to anything cultural that might explain it away. If I truly imagine drowning something in a bathtub it's quite violent and sick. Sans cultural referent, I have to wonder at the mind that would dream it up as a metaphor for anything.
So, no, I'm not happy. It's disturbing that such rhetoric enters into the parlance of government officials and candidates to office. I don't get the sense that your choice to not vote for Norquist comes from this indiscretion, nor that you even find it an indiscretion, but you're certainly entitled to your opinion and this dead horse seems pretty well beaten.
Which is, itself, a messed up phrase.