I used to practice tai chi every day. I was pretty good -- I did yang style short form and sword form. I had a big wooden -- obviously brown and wooden -- sword that I used, and would often practice in the pool area in my apartment complex, since it was the only place with enough room and it was almost always deserted. (There was a much more popular pool in a different part of the complex.)
I was practicing one morning when one of the security guards came by and watched for a few minutes. He asked what I was doing, and I explained what it was. If you've ever seen tai chi -- even sword form -- you know how slowly it moves, more like a dance than a martial art. The guard laughed and explained that he had gotten a report of a "suspicious person with a weapon by the pool," and could only conclude they meant me, I laughed too, but later on when I thought about it, I realized that had I not been a small white woman -- had I been a big African American guy, for instance -- they would have just called the cops, and I would likely have been arrested whether or not it was obvious my sword was wooden and basically harmless. Or, worst case scenario, shot.
That particular amusing anecdote no longer seemed amusing after that.