Extreme left is probably not quite right, "totalitarian left" would probably be closer to the mark. A left that considers all its views and actions beyond question and wields social justice ideas as weapons against dissent. For example, remember how every criticism of Hillary Clinton the neoliberal warmonger was and still is blamed on misogyny? How Sanders and his supporters were smeared as sexists and racists and al…
The thing you're talking about is not Leftism, it's Identitarianism. Remember, the left-right dichotomy is about how the means of production should be owned and controlled. While the Left does also stand for such progressive causes such as anti-racism and anti-sexism, the contemporary Liberal/Clintonite strain of Identitarianism doesn't have much overlap with actual Leftism.
Back in the day the left-right thing happened over who backed the king of France or not, by where they physically stood in the room.
And it was very much a social rather than economical thing back then.
Keep in mind that right-wing has often been used synonymously with conservative. As in preserving the social status quo of classes and whatsnot.
Later on, with socialism/communism coming into play, workers parties and traditional leftist parties found much common ground.
In Norway we have this "hilarious" situation where we have two parties names Venstre (Left) and Høyre (Right), whole both are to the right politically speaking of Arbeiderpartiet (Workers Party).
BTW Venstre is a bit player in Norwegian politics these days, while the biggest parties are Arbeiderpartiet and Høyre (the two taking turns leading the government in cooperation with various smaller parties).
During the last 4 years Venstre has even acted as a underwriter of the Høyre lead government, even though they keep voicing disproval of their actual policies.