If I have to get a read on someone before I directly interact with them, their wearing of a MAGA hat will give me a bunch of useful going-in assumptions, just like any other political insignia worn as clothing.
Where we disagree is this:
1. You don't have to get a read on someone before interacting with them. That path is the path to stereotyping.
2. We disagree on whether those going-in assumptions are useful.
The burden is on you to “give him a choice”
If someone is wearing a Boston Bruins jersey in public, I think it's reasonable to believe that they're a fan of the Boston Bruins hockey team. I _could_ ask them if that's the case, or if they're a New York Rangers fan that's wearing it ironically, but that would (probably) be wasted effort, because I have a good idea of the answer I'm going to get.
It seems reasonably straightforward to apply that to other team insignia, especially one that is so clearly affiliated with a specific political leader, and their political outlook.