When I took ballet, I wore the dance belt, but since then I never wear the dance belt. In fact, I go entirely naked underneath. I never wear any underthings under any of my clothes, ever.
When I am in class, my penis, balls, and ass are pretty plainly visible. There are some stretches that you do that stretch the fabric so thin it becomes transparent. But no one minds. No one has ever shown me the slightest misgiving and I've been attired like this for 2 years now.
I have seen women in class who are similarly dressed. I remember one young lady in red lycra bike shorts, warming up before class. Lying on her back, she hugged her knees up to her chest and rocked back and forth. This position exposed her buttocks and crotch; the red fabric stretched so thin it was transparent.
She wore no panties.
Her most intimate female anatomy, her anus and vulva, were clearly visible in full detail. She felt no shame or inhibition but kept rocking, exposing her womanly private parts to everyone. This is just one example, there are many others.
If it's all right for women to go naked under their tights and leotards, why not men too? You don't need a dance belt in yoga class. You don't need a dance belt if you're not dancing. Why not go out shopping in your leggings without anything underneath? Women do all the time. In the warm weather, women go braless in their sleeveless tops so that their bare breasts are on display to the world every time they reach their arms out or bend over. Men are not exposing their penises openly, so if they're covered by leggings, what's the problem?[/i]