Sparkles and Ponies, and Dolls oh my!

Ok, so my son loves to draw and paint , and most recently- sparkle....everything and anything. He's 2, and is learning all about different textures and shapes and colours , through creation and exploration. Yeah, I'm one of those mums who's house is like a Montessori school. Right now he's working on his ornaments for his friends- we made salt dough ornaments and he's to decorate them for all of his little friends as their gifts. All he wants to do is apply sparkles, it's quite entertaining.
My son also has a baby doll, which he calls Baby. I got him a doll in the summer time, to teach him how we take care of babies, seeing as I was having one [back in August] and I wanted him to be ready. He didn't show much interest in the doll until recently, and now the baby goes with him everywhere. He tucks her in, he puts her in the carseat and makes sure she's warm, he even 'breastfeeds'...via his collar bone. I gave him a bottle to feed his baby with, but he prefers the mama way (according to him). It's absolutely adorable and heartwarming- in my opinion. My brother-in-law came over today, and is adamantly against this. He just had a baby boy recently and is a first time dad, learning all the tricks of the trade- he thinks it's totally inappropriate for a little boy to have a baby. Well- I think kids should have an opportunity to play with whatever they want, be whoever they want, and become whoever they want. Gender-specific toys/activities aren't going to change someone's sexual orientation, it's just going to frustrate them even more. Why should boys have to play with g.i joes while girls play with Barbies?
My husband wasn't too impressed today with my choice of toy for my son, from McDonalds.. I chose the "girl" toy, because it was a My Little Pony, and the boy toy was some weird looking robot thing...that my son would have no clue what it was. He knows what a pony is- he doesn't care that it's pink or purple or whatever colour it is. It came with stickers, and a hair brush- he was in heaven. What is it with men, and their phobia of all things natural?? It's not as though my son only plays with these types of toys, he's obsessed- OBSESSED with dinosaurs and trains, loves cars and lions, and teasing the cat. He loves to kick a ball, jump and play...so why is it that my husband- and my brother in law (his brother!!) feel so uncomfortable with a baby doll, some ponies and sparkles? My son is 2....look out- I think he's on his way to become the next Dancing Queen.