i feel that everyone person should dress nicely in clothes that makes him/her comfortable and so they are not constantly looking at what other people are wearing and being all self conscience of what everyone else is wearing!
i believe there is nothing wrong with tight pants if that’s what makes him comfortable and happy leave him and let him wear it!
as long as they way someone dresses isn’t changing which will cause him to change his environment and his actions obviously in a negative way. i would say leave them alone! they are just trying to fit in which is perfectly fine!