This is beyond just intolerance of the intolerant, it's a sick worldview. I'd like to repost here a Reddit comment which I found to perfectly capture what is wrong with the so-called regressive left:

Social Justice Warriors are also referred to as the regressive left because they are regressing backward from liberal society to defining people based solely on their identifying group, be it race, gender, sexual orientation, ethnicity, or religious belief. They simply rationalize their bigotry differently; the bigoted right separates people by these lines but think that everybody should conform to the majority/dominant group. The bigoted/regressive left also treats people on the same lines but think that those in the dominant group should give special privileges to those in the minority in order to equalize.

This is also an important distinction. It isn't that they are just overzealous on equality; I don't think that's necessarily possible. They have redefined equality. For most of us, it has always meant equal treatment of all individuals by setting a single set of rules and judgment based on individual merit. The liberal ideal is to not even care what color, gender, religion, sexual orientation, or other personal identifier a person has, unless it is directly relevant. Thus which group you fall in is generally irrelevant. That you happen to be born with a certain skin color then gives you no personal benefit or hindrance.

The regressive left defines equality as a bulk statistic over the whole of an identifying group. Which group you fall in then is critical to how they treat you, the same as far-right bigots. (They only differ on how they treat each group.)
If you are white and male, for example, then you are seen as privileged because, statistically, white males have more wealth and power. That you may individually have no power or wealth is irrelevant to them, as if there is some big party where all the white males all go to divvy up the loot and push a single common agreed interest. By this reasoning, a homeless American white male murdered by police (like Mark Kelley) is privileged; a billionaire African black woman (like Isabel Dos Santos) is not.
To these regressives, the idea of not caring what somebody's personal identity is (such as race) is abhorrent. They don't see their blatant racism or bigotry, largely because they think it's ok as long as they're rooting for the group that is statistically an underdog (even if the individual isn't).

When challenged on this whole bizarre re-definition of equality, many will dismiss it as "reverse racism", meaning it's only racist against the dominant group, so who cares. (Again, regardless to the actual circumstances of the individuals.) But this is, of course, mistaken. They are stereotyping all people based on the groups they fall in, and dictating which groups are allowed to do what, across all groups, and to the detriment of many in those groups. Muslims are seen as oppressed in the West, so the regressive left oddly supports the conservative Muslims to oppressive other Muslims, like separating men and women, because that oppression is just part of their culture, which is an underdog in the West. So if you are a liberal Muslim woman seeking equal rights and treatment for Muslim women, the regressive left will actually fight against you, even trying to get you banned from speaking at a university.
It's this perverse redefinition of equality based on bulk statistics that leads to such bigoted reviews that the regressive left ends up with many of the same policies as the bigoted right. A fundamentalist religious group on the right in California sued (and failed) to have yoga removed from schools as a violation of their religion. A regressive left student union successfully stopped yoga classes at the University of Ottawa under the guise it is "cultural appropriation".

At Missou, the activists demanded blacks-only housing so that they could explore their culture. Racists on the right also want blacks in their own housing. In the UK, student unions have supported the right of Muslims to separate men and women in lectures as long as they are the same distance from the front. "Separate but equal" was also a policy of the American racist right.
The regressive left, led by Anita Sarkeesian, wants to stop sex and violence and scantily clad women in video games. The religious right, led by Jack Thompson, have long fought for this as well.

Same policies over and over. Just different rationalizations.
They aren't just an extreme version of the left; they've abandoned liberalism for a form of underdog authoritarianism via stereotypes.