I agree it's not even the crime of the year but (assuming he's guilty) CH went out of his way to commit a crime and I don't think that's the sort of person I want looking after the country. Worse, he's enough of an idiot that he got caught doing it!
Pretend for a moment that he's someone you are looking to employ, he turns up at the interview and you find out he's got a driving ban, a conviction for perverting the course of justice and hasn't long gone though a messy divorce because he had an affair. Would you employ that guy?
I think most of us wouldn't employ someone like that without very good reason but somehow it seems it's more forgiveable with politicians.