I never thought thug was racial. More ghetto/rap than racial. I just though it meant physical bully, or brute force user.
To a young man, thug can even be a compliment. I used to despise those wankers. It seems to be more of a masculine thing. Even though those people are always ignorant ass holes, and they grow out of that after they realize that prison isn't the romanticized hardcore club that its made out to be.
You're right though, with an urban/racial context, especially for a woman, that would be quite insulting.
Its interesting how language transforms over time, and changes meenings depending on who you are and where you are in life.