Because their comment is talking about race. Why do you feel the need to take attention away from that?
And I use 'group' loosely since it is really more of a sub-culture than a defined organization.
Look at it this way, a black man that is unjustly shot by police is more likely to be shot because he is a man than because he is black. If we want to stop unjust shootings, we should focus on the factors leading most to them, or which racism is second behind sexism (and maybe third behind classism, though since class is less apparent in short interactions than race and gender, it may end up not being as big an influence until we get to the court room).
"The justice system is far more sexist than racist" - what evidence do you have for this statement?
"a black man that is unjustly shot by police is more likely to be shot because he is a man than because he is black" What about this one?
For the black man, passers by rushed him, knocked him down by force, and called the police.
For the white man, people pointed, talking loudly about "what is he doing", and one person called the police.
For the black woman, people ignored, regardless what she did to the lock.
For the white woman, people went to help her break the lock.
If random people have this sense of justice in regard to a fairly common crime like bike theft, then why should we be surprised if the criminal system have similar bias?