That's preferences expressed at an individual level. That's fine. The problem is when you say in aggregate "only girls will like this toy, you are boy, ergo you

That's preferences expressed at an individual level. That's fine. The problem is when you say in aggregate "only girls will like this toy, you are boy, ergo you shouldn't want this" and have marketing that either excludes or strongly suggests the toy you want is Not For You. See the comments in this very thread about boys bullied for playing with "girl" toys. That's the awful consequence of stupid and inane gendering.