Boys playing with dolls?

Originally I was going to talk about the "God's Will" book but we discussed something in math that really irritated me.  My math teacher asked us if boys should play with dolls and the response was of course, "NO!"  I'm not going to talk about everything he said but I see this a lot.  Ask yourself this.  It's ok for a girl to play with trucks and cars yet it is wrong for a boy to play with dolls?  Does that make any logical sense?  No!  Where are these "rules" that boys have to abide by because I don't see any book.  We still struggle with masculinity but this masculinity starts when a boy is a mere 5 to 10 years old.  They are taught by parents and siblings that boys should play with cars and girls should play with dolls.  Yet it is more socially acceptable for a girl to play with anything and yet boys should strictly play with boy things.  When boys do play with dolls everyone starts thinking that the world is going to end!  Oh my gosh a guy playing with dolls?!  Let's all take drastic measures!  Why are people so afraid of this?  Especially parents, parents are especially scared when their son does this.  What makes people freak out about this?  Honestly it makes you look like a scaredy cat.  A boy that young doesn't know what is acceptable.  When does he know?  This message is implanted in his brain by his parents.  That's mainly who is responsible for this.  Please do me a favor, grow out of this book of "rules".