IMO any decent trainer- regardless of profession- should be conveying to people that a mutual agreement of heiarachy, fairness of handling, understanding of how horses think, and mutual trust are the most important aspects of horse training and building a relationship between horse and human. If he did beat the crap out of a horse at a demo, well...
I have no problem with trick training as long as the human is made aware of the dangers of teaching a horse to do things like drop to their knees for a bow or getting them to nudge/'hug'/nod/shake etc. Following this logic, I personally don't find it appropriate to say that trick training can help people 'get on the right track' or that it is ok to tell people of 'all levels' to lay their horse down :/ If the horse isn't responding properly to basic handling, teaching it ways of effectively evading your commands isn't going to help you 'get on the right track'
I don't think you are being overly sensitive at all, but perhaps let your friend do some trick training with their horse and see how it works out. They don't sound inexprienced per se and sometimes learning from experience is best:
I was given a trick training book by an older lady who didn't do it with her own horse but thought I would think trick training was 'cute'. I felt we had a firm enough relationship that she wouldn't use tricks to be naughty so started teaching Alz to bow. Niively I was like 'what can go wrong?!' and 'when is anyone ever going to acciedntally give the signal to bow and potentially cause and accident!?' (book had something like this at the front) Well I didnt have a problem with any of the above, but the farrier on the other hand... Alli got bored when being shod and decided the poor farrier was 'telling her to bow' which wasnt too clever! So even if the horse is well behaved with its normal handler, ask: is it as well bahaved with other people in testing situations!!
I learned from my mistake and no one was hurt but it certianly made me more aware thet trick training isn't easy or suitable for everyone!