Parade routes are generally closed off and only people who want to be there show up. If you don't want to see what's in a parade, don't go to one.Or you could put some of that stuff behind closed doors. You know like decent mentally healthy people tend to do.
People in general have a bad reaction to certain things being flaunted in public, so it's not just directed at the alphabet crew. In fact, local/state laws are pretty strict on things like strip clubs, etc. Yeah, I guess you can hide behind it is a free country. But if you are doing it in public I believe it is also a free country to ridicule you for it.