We struggled quite a bit with this question. I think our initial instinct was to be a bit militant about it, but the reality is there is so much of this in our society that unless you're willing to go full Captain Fantastic they will inevitably be exposed to these types of things growing up. It happens through relatives, well-meaning friends, birthday parties, school, media, etc, it's impossible to try and weed it all out. I guess now we take the approach where if someone gives them something we wouldn't, we don't make a big deal about it, especially not in front of the kids. Kids are very malleable and fickle, and as soon as they forget about it(maybe an hour, a day, whatever), we just throw it away. We do make it clear to our immediate family what we don't find appropriate, but at the same time, we're fully conscious of the culture we are a part of. It's not necessarily an easy line to walk, and there isn't really much guidance out there, but we feel it's important to be strong in our course, without being so inflexible given the realities.

In my experiences growing up, if something was fully restricted, it made me: a) really want that thing (happened a lot with tech) b) develop really unnatural aversions to it (a religious upbringing made this rear it's head in a lot of plays)

So my (completely amateur) opinion is to have a policy like you're doing, but only enforce it like 80% of the time. 100% is where you start to get into giving people complexes territory.

You might cause backslash in other direction if you are too militant. Ultimately, kids want the same as other kids have once they go to preschool.

Also, the association between apparently girly and bad or dumb is not healthy if you happen to be girl.