I've never had an issue like that, but we also get the "tech in training" most of the time. (Ticheli is the local "angry" cat. "Angry" because he puts up a whole lot of fuss and flail, but doesn't ever put any tooth or nail behind it. So we get the techs that are still learning how to handle an angry/scared cat, which includes a lot of fun vet comments like, "Okay, if that cat was REALLY angry, he would have bitten off your finger, so don't hold him like that." or "Do you WANT him to rip your face off?" LOL!) Anyway, I don't know if they just know better than to make rude comments, or if they are too new and scared to say anything. LOL
To add something constructive, I'd agree with GO, and just ask not to see that tech on your case. And I think that writing a letter is completely reasonable!