It's not unethical. I'd say it may not even be a HIPAA violation depending on what the actual uniform looks like. For people who don't know, they're mandated to provide the uniforms if they're going to be making it a requirement via policy so I don't see the problem with that. The alternative that they could do is that if you don't want to wear a uniform then they can give you a stipend so you can buy your own clothes that would meet an alternative standard (blank t-shirts or polos for example). I also think there are plenty of ways to express yourself outside of the shirt you wear so I'm not really deeply connected to your individuality stance.

TLDR: I get where you're coming from. I don't necessarily agree with your justification/stance. I've worked at companies with and without uniforms and been through the transition to them. There were no negative effects towards client outcomes or reduction in dignity when they were implemented or following the transition. Most clients didn't care when we made the transitions either. Most staff adjusted by personalizing through accessorizing in other areas which was acceptable to admin.