Is there a word or short phrase to indicate the opposite extreme of “racism”?

For example, a person fights (or claims to fight) against racism in the manner of believing a group/ethnicity/etc. (in a culture where this group is often disliked) to be morally superior, and if a member of this group commits something bad, this person refuses to believe it, and calls everyone a racist who dare to say anything but praise about people from that group. Or, this person being an advocate against prejudice, and fighting for “equality”, but in fact vilifying and being prejudicial against everyone who does not share his/her exact political beliefs.

Is there an English word or short phrase, to express the above attitude in a much shorter way than that whole paragraph?

I think demagogue is not the word, because it means that a person claims to have other beliefs than he/she really has, for gaining some advantage.

The main point is not on holding some race to be superior instead of inferior, but to claim to fight against prejudice but at the same time being prejudicial (for example, by calling everyone a bigot who do not agree 100% with them).

Solution 1:

You are describing supremacism, the view that a particular group is and ought to be treated as superior. Its proponents often describe it as anti-racism, but it is actually a form of racism which often arises in the context of racial conflict.

For example, in the United States (with which I am familiar) and in other locales, racism targeting the African-American minority sometimes expresses itself as “White Supremacism” movements which claim whites are superior. These movements are countered by “Black Supremacism” movements which claim that the targeted black minority is actually superior.

Solution 2:

Those who are overly sanctimonious or self-righteous in their war against the wrong right-wing beliefs are commonly said to be (too) politically correct, or PC. Normally, this has a negative connotation, because it usually implies intolerance and superficiality.

Solution 3:

What you are talking about still sounds racist, not its antonym. The opposite of someone who is racist is someone who is not a racist, so someone who is unracist in the extreme can be said to be racially color-blind, or race-blind.

However, critics of this sort of color/race-blindness have claimed that is still a form of racism. See the referenced Wikipedia article for a discussion of this.