What's so Bad About a Boy wearing a dress?
Because the old ones have become extreme leftists out of touch from mainstream America. They ceased to be liberals. They have a left wing perspective on various issues, and then pursue politics, scholarship, culture changes based on that. They are intolerant of truly opposing views.
They are in fact left leaning conservatives.
I'll answer the question:
1. Boys and girls are different, and our society should recognize, accept, and cultivate the best of both.
2. we need order and stability in our society. That's starts foremost with cultural mores. As a country we have to stop attacking the basis of civilization itself and start reinforcing the goodness. Boys wearing dresses would be an assault on our values and order. Instead this would encourage people with stray thoughts or propensity to do strange things to do even more.
3. It's silly and perverted. We the people through our society have a right to call something silly and perverted and treat it as such without long explanation.