I was fortunate enough to go see a GM clinic just a few weeks ago. I don't know if he has mellowed out but I thought he was a phenominal clinician. In fact, there were some situations he could have really gotten after but didn't. He was actually quite encouraging and really praised people for what they did well and when they accomplished what he was wanting them to learn. He reviewed the basics and taught exactly WHY we do things the way we do. I've taken clinics with other trainers who were MUCH harder on me then he was!
In the first group (3"6) there was a heavy-set rider riding a difficult horse and he really praised her riding ability. Never made mention of her weight. In the last group (4") there was another heavy set rider. He went through the group and gave an "evaluation" of their riding ability. He really complimented her and told her that if she was more fit she would be even better. And then he turned to the audience and talked about fitness and joked around that he loves to eat but hasn't eaten much since he's gotten older. It was actually very tactfully done.
Honestly, if I had to choose between the two I'd rather have a clinician (clinician, not trainer) who was heavily critical rather then someone who didn't say anything. I'm paying for their instruction and critique so that I can learn and improve. I'm not there to feel better about myself.