Well protecting your child is one thing, but allowing them to innocently do things in social setting, without explaining the possible repercussions in time, in my opinion, isn't parenting. Don't forbid them, just explain and give examples. It is tough in today's world, because extreme ideas that reward kids that succeed the same as those that fail, robs them of the drive to find their niche in life and succeed. Explain to a boy of 6 why wearing a dress around the house and playing dolls is great at home, but it won't be accepted at school, no matter how liberal they are. The zero bullying policy is just a joke and cannot be enforced 24/7. And what is the punishment for bullying? A kid gets sent to detention for sensitivity training. It is a joke! No punishment equal to their offending action. As a young girl I wanted to wear overalls to school. My folks explained why this was a very bad idea. This was before Hollywood made girls wearing overalls a fashion statement. I didn't listen and was laughed at by everybody, even friends. I never did it again, but the bullying never stopped. One boy cut my hair in back off with his pocket knife. I turned around and punched him hard, blackening his eye. He then hit me hard while another boy held me and then the teacher intervened. I had to change schools. I was found just as guilty because I hit him first. Cutting off a piece of my hair and saying if you want to be a boy, then you need a boy haircut, didn't justify my violent assault. I heard later he had to change schools also because all the kids made fun of him for getting a black eye and dislocated nose from a girl. I have no one to blame but myself for not listening to my folks about the possible results from dressing in a way that wasn't accepted female at that time in public settings. I have never worn overalls since! This is why I fault Megan for encouraging her son, instead of explaining what might result from his decision. Don't forbid him but certainly don't encourage him. Just my opinion.
A part of the problem is that the schools are discouraging kids from being honest with one another. I wore a polka dot shirt to school once and, although I think one of my brothers asked me if I really wanted to wear that, my parents didn't have to get involved. I never wore that shirt again but, somehow, I survived the ordeal. Now, it would be all about my right to wear a silly-looking shirt rather than about the shirt looking silly. The same would be true of the shirts with the puffy sleeves. Unless you're a rock star, it's probably not a good idea. When kids are allowed to express themselves, a boy would wear a dress to school maybe once, and that would be it. A good parent (or sibling) might ask him if he's sure he wants to wear that.
Hmphhhhh! When I was about 7, it was my dear stepmother who insisted I wear a suit to school complete with saddle shoes. I won the battle against the young gentleman who thought I looked like a pansy but alas, the suit looked like it was worn by a returning civil war soldier and was given a proper send off.