Besides the obvious proclivity toward drinking songs of course.
Country music fans tend to know who they are, what they like, and aren't afraid to talk about it, no matter where they are. Political correctness is something that other people pay attention to, not country music fans. They love their country, and I don't mean just the music. They may not agree with the various policies of whoever is leading the country at the time, but they still love their country.
They'd NEVER forgive someone for speaking out against the country or their leaders during wartime (Remember the Dixie Chicks?) even if they don't necessarily support the war.
Country music may be simplistic in a lot of ways, may not rock out like Pantera, Metallica, and the rest, and may not appeal to many of you who like a little more edge to your music. But listen to Lee Greenwood sing "Proud to be an American", or Charlie Daniels sing damn near anything, or Toby Keith's "Angry American" and see if it doesn't get you fired up.
Also, if you want to know what it is to be treated like royalty, show up to a country music concert or event with anything that resembles the fact that you are on active duty in service to your country. You'll have more people thanking you for your service and offering to buy you beers than you'd be able to drink(although I certainly tried).
What I'm trying to say, in my piss-poor fashion, is that when I believe in something, I support those that do the same. I'll pay $14-16 for Toby Keith, Gretchen Wilson, Kenny Chesney, or the rest, but I'm not going to buy Green Day's album (although it does rock on some songs). I'll find other ways to 'acquire' the songs I like.
Madonna (who I've never liked, no matter WHAT her opinion was), is another example. She thrives on controversy, and has to thrust herself into the center of the public's eye. When she came out in the 80's with her initial album, I knew she was a slut for the public love and would always be. Here we are 25 years later, and I've been proven right with her every move. Never bought a Madonna anything, and I never will.