I think that this is not correct. For example, women used to be discriminated to a much bigger degree than they are today, yet with a huge effort this discrimination has diminished, and women can vote now, and soon the US might even have a female president.
I think that the case of women is a case that shows that the fight against discrimination is worthwhile.
I am not too sure which religious arguments can be used. Perhaps one could argue that Christians were slave owners, and often killed their slaves, yet their religion actually would not allow this: "thou shalt not kill",
Because of this, I would say that it is not enough to hope that people will follow their religion's call not to discriminate: instead, people should try to stop discrimination.
