I personally don’t think it’s a big deal, guys are simple creatures they see something and they act accordingly, there’s no malice in their behavior. nadz, I would say you should get over it and be thankful he buys you clothes instead of beating you.
Personally, if I’m buying anything for the lady, I go with the smallest size, yes it’s a pain for her to go and exchange it, but it flatters her that I think she’s that tiny. <— I am not a simple person, very chalaak.