This story is an example of liberalism going too far.
Whether we like it or not, there are things that appear harmless on the surface that are considered taboo in society. Males wearing dresses is one of them. If an adult male chooses to buck societal conventions and wear a dress in public, that's his choice as someone of a mature mind. He likely understands that there will be negative consequences for doing so, and has made the choice to do it anyway.
People are going to tease him. People are going to reject him. People are going to talk about him. Sure, some people may applaud his "bravery", but such people are probably going to be in the minority. For the most part he will be treated as a joke. Whether it's right or not is beside the point; it's just the way it is. It's human nature.
And again, he probably knows all this. He has the life experience to understand the risk he's taking for choosing to do something that's not considered normal. Since there's no law against men wearing dresses (in most civilized places anyway) he is free to make this choice. If he's willing to accept the consequences, hey, more power to him.
The same cannot be said about an immature-minded child. As a five-year-old, he lacks the wisdom and life experience to understand the consequences of his actions. He's going to be teased and rejected at a time when it's probably most important for him to be accepted. This poor kid is looking at a lifetime of issues and his boneheaded father isn't doing him any favors by supporting it.