As I said.. "as far as I knew"... I'm not a MOT technician.
Probably the reason people in your profession are looked upon as "grease monkeys" is because of the vast number of cowboys that your trade employs.
You only have to look in your local KwikShit for a fine example of "professionals" (granted, there's one or two that are good.. but come on.).
And then you have idiots like I had to deal with, who could easily have wrecked my car if I hadn't stopped as soon as I noticed an issue. Even main dealers can be a right handfull of donkeys at times.
I believe I'm right in saying that 3/4 of garages offered sub-standard service to its customers according to Which? magazine.. so there must be a fair few dodgy individuals out there, even if the survey may a bit one-sided.
But like you say, on the flipside, there are really good mechanics out there and it's good to shop around...
But come on.. he's not targetting you, and he hasn't blasted the MOT test station either
Respect has to be earned - it's not a given imo. But you also need to respect people's right to query any work done by any professional, in any field.
(ps, I'm in IT, and trust me, being called a "nerd" or "geek" and treated as if your a lower-level, useless employee that knows feck all, when offering technical support for some big-shot salesman who MUST have flash on his new iPad is pretty shitty too mate - so I can understand your frustration 8) )