That's awsome! 
Now, that kid is just five and growing and won't necessarily wear dresses for the rest of his life. Could just be a phase that he's going through and after a while he'll throw the dress away and act like "normal". Not saying that continuing to wear dresses is a bad thing - a bit unusual perhaps but the world is driven by unusual people - but there's nothing saying he'll be burnt forever or something. I wore dresses when I was a little kid - well, at least at home so I wasn't that cool - but that was only for a short time and instead of panicking and telling me it was wrong my mother gave me more old dresses from the attic, she even gave me some jewelry. 
Colourful stuff. Mm, good times, good times. Anyway, that was just me having a chat with my feminine side (every man has one) and I've had those several times during my life (played with Barbie and stuff, loved Sailor Moon and still do, often creates female characters in RPG's etc.).
I'm no shrink or anything but I think it's just healthy to let your "other" side out sometimes instead of hiding it in fear of becoming gay or something. It'll just make you more secure in your sexuality, I think.
...
So, uh, I don't think there's anything terribly wrong with what that dad is doing. Wearing a dress himself might be a bit extreme but he's fully supporting his kid and that's what matters the most.
I can't see myself wearing a dress in public like that, but i could possibly do it at home. I'd let my child wear them and then wait and see. If he continues to wear dresses after some time has passed then I'd try to figure out why he prefers dresses. The reason for him doing what he does is much more important to me than the fact that he wears female clothing. I don't know if I believe in gender equality, or even understands it, but I really don't believe in the old gender roles either. We are all unique and it's important to be able/allowed to explore ourselves so that we may understand ourselves and feel comfortable with ourselves.
