The purpose of an analogy is to simplify something that's too hard to understand for the person you try to convey your idea to. Sometimes analogies are appropriate, e.g. when you teach something. When you want to convince somebody whose opinion is very different from yours, analogies aren't appropriate. They sound condescending: "because you are not smart enough to understand the real rationale behind my opinion, here is an oversimplified argument based on analogies I made just for you". The question is, did Torvalds have any real argument back then? Maybe he fell back to using analogies for the lack of any real argument.
> In this case, he was trying to convey the idea that the risk is so small and so remote that it really isn't worth spending a lot of time on.
To convey the idea that the risk is very small, one needs to have a proof. Real proofs shouldn't involve analogies. They should use facts and logic.