I'm all for the 2nd Amendment, but unless you're an on-duty cop or FBI agent, open (un-concealed) carry is VERY tacky, and looks very retarded.
I have no problem with cops harassing these open-carry guys, because I seriously doubt these guys are showing off their guns for "constitutional" purposes. They're just looking to show off, plain and simple. "OOOh, look at me, I'm a cowboy, I've got a big bad gun in my cowboy holster, look at me everyone!" What a bunch of losers. I would never EVER carry any of my pistols like that.