It can be soooo frustrating and I don't think you're over-reacting at all.
I found training with Kilby really hard. She is soooo smart and had the basic commands down by her 2nd or 3rd wk of puppy class. The problem I had when she got a little older was that because she knew how to do the commands she would only do them once or twice and then it was boring to her especially when there were so many other dogs and people to distract! I tried everything, including walking her the 8km to class (she was about 2yrs when I started that) but it made no difference, once she saw the other dogs, she just wanted to play!
The school we took her to was positive but some of the "trainers" just had no idea about boxers. Kilby wasn't food oriented so I sniggered when some of the trainers tried to tell me I just wasn't USING the food reward properly, they stepped in all over-confident only to have her spit food back at them (she is REALLY cheeky).
Another suggested that I wasn't praising her enough so to use words/attention when she did something right. I tried to explain that would make her MORE hyper but again, they knew best. When she sat for the trainer he gets this high-pitched voice "good girl rah rah rah" then he bends down to pat her (I told him not to, I could see her tail going nuts and it was like she was hovering!), and sure enough she jumped up at him and he got the top of her head to the lip.
Finally they basically told us that she wouldn't pass the 3rd level unless we completed training wearing a gentle leader. I told them I wasn't interested in that, I was at school to teach her on a flat collar and lead and was prepared to work harder and if they couldn't help me, I'd find someone who could. I don't have anything against halters but for me training is about teaching them how to behave without that sort of thing.
Anyway, after months of frustration with their methods (and sick of being the one they always pointed out as a 'problem') I just started trusting my gut and doing what worked at home... taking toys to class (yes, I got VERY strange looks as I dangled Santa's head in front of her ;p) and that worked well for her (mostly). I also decided that I would do as much of the group training as she would tolerate but I also wasn't afraid to walk away from the session for a few minutes if she was really acting up (other times she just looked so bored she lay down!). I think this also made me feel more confident and she picked up on that mood too.
Wow, sorry, that was long. The main point I wanted to make is that I think you're doing the right thing by finding another trainer that works for you and your baby. Each dog is different and what works for one may not work for another. And to be honest, if I was in a group and saw a trainer do that to a dog, even if it wasn't mine, I'd change classes too.