So, I have no doubts that the marketing departments of companies that decide boys on TV playing with their toys should always be hyper-energized and out for the kill, and that girls have to play with things that feed a maternal instinct, try to set the stage to make sure that there are toys specifically for boys and ones just for girls.

Now that sucks, but you know who can help? Parents. Parents can help their kids realize that they can play with whatever they want and it does not reflect on their sexuality (without having to explain sexuality to a 4 year old). Parents can ask their boys if they want a toy that just happened to be marketed to girls. And if the kid says "No, that's a girl toy," they can ask them why it's a girl toy and talk about it. Parents can scoff when they walk by a Nerf stand that has pink Rebelle crossbows, and when their kid ask why they made that sound then they can explain that having to make something pink so a girl will play with it is stupid.

It's not uncommon for children to not listen when told to do something like brush their teeth, pick up their toys, or stop calling their siblings names, but they'll take in almost everything you say when you're just having a conversation (whether you want them to hear it or not). Talk to them! Wherever the influence is coming from: books, TV, music, movies - figure out what they think it's about and talk to them about the message you think they should be getting from it.

As for the toys thing: if you're a dad with boys, introduce female characters into the toys and the games you play with them. Let them see you play with them, and maybe let the girl save the boy every once in a while. I'm not saying don't give your sons trucks and don't give your daughters dolls, but call out the bullshit ads on TV (all of them for that matter, not just the toy commercials) and let them see you not buying the message they're selling. You may actually make an impact, and break down some of those barriers that marketing departments do their best to put up. And even if your boys don't end up playing with barbies, maybe they at least won't tease the boy that does.