I don't personally think you're being unreasonable.
Your DS is responding to something that is troubling him in the only way he knows how. For him, it's crying.
Does he cry too much? Maybe!
Should the teacher respond to his crying by saying; "you cry too much?"
No, I don't believe so.
When my son was 7 when I was approached by his teacher whom felt he had some special needs. He cried a lot too. He truly couldn't help it and it was because he was overwhelmed and not coping. This manifested into full panic attacks eventually. When my son was 9, he was diagnosed with Autism, sleep disorder and anxiety!
We all shouldn't just assume that they cry too much because they're sulky children. My son has been in and out of schools since, because a lot of teachers lack compassion for children that need a little extra support. Some children become a burden to said teachers. There's plenty of wonderful, attentive teachers too, of course. Thankfully, my son is now in a special needs school. The teachers are wonderful.
My point is, it may very well be something you need to worry about, regarding his teacher. There might be further reasons behind your son's emotional reactions. We really are not qualified to say because we just don't know the in-depths of your circumstances, really.
I would absolutely speak to the teacher. I would ask her if he cries too much and whether this is something that is concerning her, as your son had mentioned that she had made a comment about him crying too much. Just make it clear to her that if she feels he cries too much, that you would like to get to the bottom of why. Work with her on this.
Good luck.