I never really saw the point of examining the root cause of anything. I usually don't care in all honesty.
So to me

Therapist = this sounds like old stuff from your mother
Me: Well Duh -but wtf - what difference does it make?
Therapist: What do you think?
Me: I don't think makes any difference at all.
Therapist and me = THE END

But
It may be that part of it is seeing irritation happen from someone isn't fatal in general or fatal to that relationship. You and your husband get irritated with each other. You and your daughter -= it isn't fatal to the relationship. The same is true of this guy and you - it isn't fatal on either side.

Plus if he actually does have mostly athletes of some sort = they are often not crushed by clear non-emotional direction - they hire him for that. I find that true of students I have who are athletes - I love to get athletes and theatre people -they have dealt with losing, criticism of response, and competition and I don't often upset them. Some of the other students I just tell to drop my class because I am never going to be the hand holder they want.