Mary Ellen wrote this, then this, and this. You should read them and the comments or my post here may not make much sense.

I blame it all on the women's movement!! Ok, I say that tongue firmly in cheek. But not completely. I think we're at a crossroads in our social evolution. We're at a point where wonderful, thinking mothers, like Mary Ellen, are saying things like this...

"Each of my daughters went through a stage of wearing only dresses and a stage of refusing to wear dresses. They are lucky. Boys don't get to make that choice. Unless they live in Scotland."

And she's right. Generally speaking boys today don't get to decide to head out for the day in a dress. And frankly, most probably don't want to. Maybe this is because they have been raised to believe that dresses are the sole territory of girls. But I bet if they all did go out in dresses many, dare I say MOST, would decide that dresses aren't all they are cracked up to be.

Anyway, the crossroads. Here's the thing. We had the women's movement. Very handy, now all the women can wear pants, play sports, have equal this and equal that. I know I'm being facetious. But I'm only 27. I've enjoyed these luxuries my whole life and didn't have to work for them at all. What can I say, I'm spoiled.

So we're in a post-feminist-movement time now where there is the firm belief that a woman can do anything a man can do as well if not better than any man out there. Which is super great for women. But not so great for men.

Now we've reached a stage where men (or us mom's with boys who will someday be men) start asking themselves "If girls can wear pants, why can't boys wear dresses?"

The truth is they can. Absolutely 100% CAN wear dresses. But there will be people standing in their way. In many cases the first people to stand in their way will be their own fathers who would never think to want to wear a dress.

But is that any different than the first women who started wearing pants? I honestly don't know, I wasn't there. But if I were to imagine I would guess that the first women to start wearing pants outside and around in society got the same kind of reaction as men in dresses do now.

Society would probably assume that she was confused, ill, homosexual, a rebel, trying to get a reaction, stuff like that. Her biggest opposition would probably have been other women, particularly older women who wouldn't even think to have done such a thing. As more women started wearing pants on a regular basis I bet all sorts of hell broke lose.
But in the end. Women wore pants, dresses, skirts, shorts, whatever they like. And I think men can, and possibly will, eventually do the same with dresses. But it won't happen unless they want it. It won't happen unless some (and then more and more) are willing to make the first move. And I don't think it will start with little boys in dresses. They're too fragile. It will be the teens and adults who have the conviction that men can do anything women can do AND wear a skirt.

If we really feel that your sons should be free to wear pink, wear dresses, and whatever other things we think they have been denied. Then why not just do it? Change can only come about by doing things differently. It's not going to make a difference at all to sit around and whine about it.