My main concern is whether it is causing difficulties for him at work, school, etc. Do his friends accept it? If there are no problems, then I don't see anything wrong with it. Otherwise it might be best to wear women's footwear only at home. My wife accepts my wearing women's boots and platform slippers in the house, but not in public. This is good enough for me since the reason I wear women's shoes is for sexual stimulation. I don't necessarily want to let the whole world know about it!