Boys will physically assault boys who like pink. It'd say that counts as "people concerned that boys don't display their liking of pink".
Also "like pink" is different from owning the occasional pink thing. I suppose a boy who would dress exclusively in pink would stand out, and maybe the bullies would try to cut him down. Still, I suspect it is not a large scale problem - obviously I don't condone the actions of such bullies, I mean there are probably not that many boys who would prefer to dress all in pink. (I didn't research that, though - in any case everybody should be allowed to like/wear whatever they want).