harpy,
I know your remark was probably just tongue-in-cheek, but I must respond to it. This guy was a genuinely nasty bit of work and everyone I know who has made his acquaintance agrees (although I suspect his mother loves him). The company I work for is absolutely full of good people and "bad apples" stand out a mile. It is simply best to not have such people around in the first place.
This guy squandered any respect his position at the flying club could have earned him with a total lack of man-management skills. He's the sort of person who (as you accuse me of) would have put himself on a fast-track to management by brown-nosing and thereafter gone straight back to his egotistical and arrogant style of management - he's already done it once at the flying school.
My conscience is clear, I did the right thing. It probably won't happen again though as I don't think I know anyone else worthy of un-recommendation. I have recommended many pilots to my company, most of whom have been successful.
For anyone I knew less well or was unsure of their flying skills, I offered help and advice to the individual whilst remaining neutral if questioned by the recruitment department. I would always say that the individual seemed like a nice person and was worthy of an interview, but I could not vouch for his/her flying skills as I had not personally flown with them. This usually gave them a chance to "cut the mustard" if they could.
Being able to live with myself and get a good night's sleep is important to me, and I actually derive some self esteem from the fact that I saved my colleagues from having to put up with this individual.