This is the first I've heard of this. I've been in that McDonald's and never had any trouble. I think it's the one right behind Tryangle's but I'm not sure. Pam's House Blend reported it first. Here is the Blend article.
The ACLU says it's "representing two gay men in an official complaint to the Louisville Human Relations Commission after an employee at a McDonald’s restaurant in downtown Louisville called them and three friends a series of anti-gay slurs." The Kentucky Human Rights Commission doesn't have anything on their site. The Louisville Metro Human Relations Commission is here. They aren't saying anything either.
The ACLU report is here.