Thank you, Hanna! I appreciate the advice. I don't really feel bad about trying to help him, ONLY because my sensei has told us to help each other and give feedback. Otherwise, I wouldn't do it. I'm going to have to try it non-verbally, though, as you suggested. Thanks!
Even if it's basically encouraged in your dojo to give feedback you do still have to take it on a case-by-case basis. Feedback is meant to be helpful, after all, and if you can see from the way the person reacts that they aren't finding your feedback helpful and welcome, then I would say it's better either to try to give it differently, or simply just not to try to give feedback at that time with that person.