Girl + Truck = Okay, Boy + Doll = Homosexual?

So often we talk about wanting little girls to have the same opportunities as little boys, but perhaps in some cases boys are lacking the opportunity that girls have.  This, in my observation, is occurring mainly in play. 
Some parents are especially progressive in trying to protect their children from the ill effects of gender stereotyping, for example the parents of Sasha Laxton, whom as we have discussed in previous blogs, is being raised completely "gender neutral".  Where is the line though?

It seems we draw a very distinct line.  In the "gendered play" department girls seem to have an edge over boys. It is relatively commonplace and accepted for girls to play with trucks, participate in sports, or just generally get dirty, traditionally past times for boys. The girl is labeled a "tomboy" and not a second thought is given.
Unfortunately boys are not afforded the same flexibility.  Boys are confined to traditionally masculine activities.  Any foray into more feminine activities, such as having tea parties or playing dress up is met with resistance and often fear by adults. 
So what is it about boys being "girly" that is more upsetting than girls being "boy-y"?

Strangely enough I suspect the answer lies in a patriarchal past.  Historically, the male experience has been understood as the human experience.  For example, early psychological studies were done almost exclusively on men, then assumed to apply to all people. So the idea of boy's toys being toys for all children is not that much of a stretch for the mine. So, girls can play with trucks and no one bats an eye, but boys cannot play with dolls because dolls are feminine. Within this way of thinking, boys who are feminine are not what they ought to be, they are weak, or weird, or homosexual, but one things if for sure, they are not normal and this makes us uncomfortable.
Or perhaps what causes discomfort is that we don't know what they are.  We have the word "tomboy", but there is no word for a boy who likes to do "girly things" that isn't derogatory.  Boys who like more traditionally feminine activities are subject to names like "pansy" or assumed to be homosexual earning any number of slurs. Perhaps we are limited by our language in this way.  Since we have no way to describe these behaviors in a positive way we assume they are bad and must be curtailed.
But what do you think? How is being a "tomboy" different from a "pansy"? Share your comments below.