A neuropspych DS 3.8 saw a few months ago used the phrase "curriculum of 3 years old" to reference the processes of developing increasing social and emotional competencies. I try to keep it in mind when talking with the preschool about strategies to manage intensities while allowing for creativity and curiousness. It's been helpful for me recently. Crying and using bodies instead of words to express emotional states is a normal phase of learning how to deal with environment and the people in it. It is our job and that of the teachers we entrust with our children to help them move forward, to use and rely on more socially acceptable means of expression and assertion to navigate circumstances. I would hope the teacher(s) would be working with all the children (including your son and the other boy on this - not just picking on your child). Labels are punishing and should not be tolerated, especially by adults. If the teachers are encouraging you to help "bully proof" your son, I might ask how they would recommend you do that, and in collaborating with them maybe they'll be less reluctant to take your suggestions seriously.
I recently brought in an emotional literacy curriculum for DS that he is allowed to do during rest time. I hope this will help but we'll see. I meet with the preschool often (probably about every couple months depending) to talk about progress and ways to keep him engaged. Intensity is a great thing if appropriate situational moderation can be achieved. It's been important for the preschool and I to work together.
Good luck!