My wife used to be a bartender in a somewhat rowdy country/western bar in Durham, NC. I used to go there and hang out at her bar to make sure the customers didn't get too pushy with her (the bouncers had their hands full).

While it sucks to be denied entrance, I'm almost certain it was to avoid a bar brawl. If you go in wearing something that they feel is likely to incite the regulars into a fight, they simply won't let you in. Sucks for you, but it makes sense.

No big deal. You found a better place to celebrate, anyway.