Perhaps it is because I don’t use Twitter or use Facebook much, but I am unaware of what you have in mind by the “regressive left.” Can you give me some examples of what you have in mind?
The regressive left can be understood as an amorphous term that categorizes the perversion of liberal ideals in the pursuit of decidedly illiberal ends. One general example could be the Title IX injunction that was sought in the case of Laura Kipnis or the “shouting down” that two professors received at Yale University for penning what many considered to be a fairly innocuous letter about Halloween costumes. In the sense this comic intends it, Regressive Leftism weaponizes social movements for the purposes of personal self-aggrandizement.
However, I feel compelled to add two qualifiers to this response:
1. I believe the effect of the “Regressive Left” is largely overstated. I don’t think it’s very widespread — I suspect they are just a particularly vociferous, yet small, group.
2. There are some other connotations of the term “Regressive Left” that take aim at defenders of moderate Muslim populations. In this sense, the term is used to label someone as an uncritical, unthinking apologist for the “evil ideology” that is Islam. Some prominent individuals who use the term in this way are Sam Harris, Bill Maher, and internet show host Dave Rubin. While I don’t suspect these people are motivated by bigotry, there are some folks in online discussions who do come off as being slightly racially charged.
I, personally, am not very comfortable with this usage of the term, as I tend to be more sympathetic to the case of a moderate Muslim majority and, as a practical matter, view blanket condemnations of Islam as counterproductive.