The Double Double Standard

As you all may know, I sell Thirty-One Gifts.  I have tons of it in my house and have bought my kids numerous things.  The products tend to run a little "girly" so H has gotten way more of it through the months than B. Yesterday, B, who is now 10, said he wanted a tote. I had a special to use, so I said "Sure! Come look and pick the one you want." These totes come in all different colors, and I was expecting him to choose red, or black or camo.  He chooses the Pink Pop Medallion.  I seriously thought he was joking, but he wasn't. He really wanted it and when I said "but it's pink!" he said "real men like pink".  I told him to pick something else...his second choice? Party Punch -another undeniably feminine pattern.  I was about to refuse. Then I thought...
What if this were my daughter and she wanted to pick camo or black? I wouldn't think twice and if anyone told her she couldn't have those because she was a girl I would have told them to stuff it - probably not so politely.  I have always been a strong advocate for my daughter that she can do what she wants, wear what she wants, whatever makes her feel comfortable and confident...she's never been a "girly girl" so that is a battle she and I have been waging a long time.
But B...not so much.  He wears what I buy him and other than mismatched socks (which have now apparently become the fashion) his "self-representation" has been fairly standard. When H got a blanket with a flower on it, he got one with a baseball.... no fuss, there. As I pondered his choice of totes, I realized that to my utter dismay I did not want my son to pick a "girly" pattern - I really wanted him to pick something more masculine.  Why was it my instinct that H can be/do/choose whatever she wants, but B should be/do/choose "boy" things? Because I'm afraid he would be picked on...I was going to pick on him about it---I kind of DID, without even realizing it - "You want WHAT?!"
So why the double standard, I'm wondering? Why are these things so deeply ingrained in us that, unconsciously, we make assumptions and judgments based on gender alone? and it's no wonder that things in this country, like civil rights for all, move so darn slowly.  I have spent all of my adult life opposing "norms" that diminish and make one person "less" than another - and I will go toe to toe with anyone about racism, gay rights and women's rights...but have my son choose something Pink?! I had to actually stop myself and think - "if this is what he wants, why can't he have it?" and "For goodness' sake, your his Mother - be supportive!"...He got Party Punch.