Okay obviously I don't know you or the other poster that complained about Universal's employees and thought it was the shirts being worn that prompted such behavior but come on man!
Back in the days working as a cast member I had the opportunity to work Guest Relations at the Magic Kingdom for about 3 months. I can tell you that I heard stories such as yours, and worse, on a daily basis. People would come in and tell elaborate stories about cast members cursing, chewing gum, ignoring them, talking with each other loudly during shows and even shoving or hitting them.
Working in attractions, both as a regular cast member and also a lead, I have been on the other side of the complaints. I have had to tell a man to remove his hand from the space mountain track at unload only to receive a guest complaint from him later that day. I have had to tell a couple to please be seated in the Carousel of Progress only to have them stick their middle fingers out at me. I had to estop the attraction and go into that theater because they still wouldn't sit down. I received a guest complaint from that incident as well.
The point is, both Disney and Universal are staffed by human beings. Whether they work at Disney or Universal they are not perfect and it's getting more and more difficult to find quality help these days. It's not either company's policy to treat its customers rudely. But none of us really know what you actually did to prompt such responses from these employees. We are hearing your side of it. Trust me, it wasn't the shirts. They couldn't care less what you were wearing.
Maybe you didn't do anything, and I'm not excusing that type of behavior if it is indeed an accurate depiction of what happened. But I have to be honest when I say I question your version. I can see running into one maybe two people that rude on a bad day but what you have described is not believable and I'm sure is an exaggeration. Perhaps not purposeful but nonetheless a skewed version of what actually occurred.
If I'm wrong than all I can say is give Universal another chance. I've been there over 100 times I'm sure and have never experienced anything close to what you have described.