Similar story: a guy is stuck in snow with his car in a parking lot (this being in Canada). I stop by, and start pushing his car to help. Finally he gets his car moving, reverse without looking.. and smacks my car parked several meters away.
As for mechanics, I'm sure there are many of them truly professional and passionate about their job - when I meet such guys I'm almost in tears of respect. But many are rather just a bunch of no clue and/or professional scammers. Perhaps along with dentistry, car repair is one of those professions where you can pretty much scam anyone without risking consequences.