"New Left" is just a term, doesn't mean it is a distinctly different entity from the liberals who championed Civil Rights. The liberals now are just a continuation of the progressive ideals that came to fore in the 60s. They support and fight for the same causes: Gay rights, Feminism, opposition to patriarchy, racial justice , environmental rights etc..But as with any movement, things change over time , new ideals form.
Some Liberals who supported more rights for women and Blacks pre WW2 might have thought that the liberal ideals being pushed in the 60s were going too far, just as you are now thinking the liberal ideals being pushed now is going too far while the liberalism of the 60s was ok.
I don't agree with everything today's liberals champion, notably their defense of Islam , Islamic chauvinism and their opposition to Free Speech and their insistence that gender can be chosen rather than determined by biology. But I agree with some other liberal ideals.
What is the destruction you are alluding to?
It is certainly different, as one was adherent to one ideology, and the other interested in another ideology.
The sea-change from "I have a Dream" of a color blind society, to "Systematic Racism" is not only objectively obvious, but planted, rooted, and grown in distinctive movements with differing ends.
The classical American Left and New Left radicalism/Marxism are also not only obviously different in their creation, writing, philosophers, rhetoric, and in terms of Old Left principles/ New Left "ends justify the means" conflict.
In thought and action they are shouting "we are separate!" until it is time for an election and a coalition is needed, then most vote for whatever idea the left of the day supports today.
Why mention today? Because in the Democratic Convention of 1968 the fault lines meant something more, now hegemony and the overreaching (in my opinion) plod of the New Left has swallowed all but the remnants of more Conservative, moderate left. (Not to worry, the Tea Party started that on the right, and Trumpism may have finished it.)
You are saying that riding that strain if ideology when appropriate affords credit to the ideology, I think that's tacitly untrue friend when looking into history, like saying Pat Buchanan's jingoism or Trump's current Nationalism should be given credit for traditional Conservatism, or further out on the political lines that a Maoist who rides to power on the coattails of democratic socialism should be assigned credit . If you have a different opinion, I'll certainly read it.
After that point though, our discussion will fall apart - as you tend to support the modern left's cultural and social changes, and I am opposed to them. We will not be able to agree there and any argument would be too large to contain.
You would argue: "Potato!"
And I would argue: "Cabbage!" then would be reduced to debating what vegetables offer in terms of nutrition and for people's health. As all politics ends up in the greater spectrum.