Members of groups subjected to discrimination often decry the prejudice directed against them, and rightly so. But yet some of the same individuals indulge in unjustified bad behavior against other groups, the kind of behavior they would condemn as 'oppressive' if someone else did it to them.
Among well-meaning liberals who disavow racism and other forms of prejudice, there are some who practice the double standard of "it is all right (or even expected) for one to criticize certain behaviors, such as bigotry, coming from certain groups but it is not all right (or even taboo) to discuss the same behavior if it comes from other groups." This double standard is in itself a reflection of unfairness from those who claim to want equal rights.
Why is it that people are so quick to see how others wrong them, but so unwilling to see how they might have wronged others? We may not have the answer, but it seems that whatever minority group we happen to be members of, there is ample opportunity for self-examination.