The vet has said he is young and unneutered so he has probably just wandered off.
As for the comment made, I'm sure it was tongue in cheek although I admit offensive to us cat lovers. For the record I have seen a LOT worse comments re cats on that forum, there are some real cat haters on there, one in particular who boasted about her son having killed several neighbourhood cats just because they had entered her garden. Whether it was the truth or just to wind people up I don't know. The best thing is to ignore idiots like that, they thrive on the attention.