I'm going to avoid the military clothing discussion, but the baseball uniform thing made me think of something:
I work in a children's library and on weekends I often see little kids come in after practices or classes in various uniforms: martial arts, baseball, soccer, ballet, etc. No one thinks twice about it because they're just little kids. But as has been mentioned, people think adults in martial arts uniforms are, at the very least, silly. What about adults in other "sports" uniforms, like baseball or soccer?
Would the 45 year old waiting for the bus be ridiculed for wearing a jersey, shorts, shinguards, cleats, etc., carrying a soccer ball?
I don't think so. When I played soccer I had no qualms about stopping for gas or running into the grocery store in full uniform, whereas I've already mentioned I won't do either of those things after karate without taking off the jacket and belt.
I'm just curious now as to why that is. I guess because a soccer or baseball uniform is less likely to draw attention as they're more commonly seen?