Freedom of speech does not mean that you can say whatever you want without consequence. That is not how this works.
He sounds like a horrible person. I think tweeting these things speaks to, at the VERY least, horrible judgment.
I am overweight. I don’t wear yoga pants but I wear very similar types of pants. I can wear whatever I damn well please. They are comfortable. I don’t wear clothes for you, I wear them for me. To quote my model-body teenager self who could “nicely” wear yoga pants before getting sick and blowing up: “bite me.”