It's not. If he never knew her and saw her on the street, he wouldn't know that she was gay or straight. The same doesn't go for a black person. The hatred for them is dumb just like the hatred for black people is. But get the fu*k outta here with that sh*t. Seriously.
Not understanding your point...but maybe I'm slow
In the extreme case, that I MIGHT have some common sense....Let's look at the facts...
#1 He clearly knows she is Gay
#2 He Knows she is his Sister's Girlfriend
#3 He has already attacked her previously
Now I'm going to put my slow bus helmet on, and go back to drooling in the corner..ohh wait...I wanna Rhyme....check me out!