Harvard maybe, or the New York Times, or NGOs or what?
No, No, No - None of the above.
Un-ask the question - it is badly formed.
There are no Leftist 'ideas' - there are only oppositional slogans - slogans in opposition to Christianity, tradition, decency, patriotism, natives, men... stuff like that.
They are not ideas, because there is no requirement for cohesion or internal consistency or consistency between the ideas or anything of that sort.
Leftist 'ideas' are not ideas: they are just slogans, sound-bites, notions, propaganda images - that's all they are.
These are so easy and obvious to manufacture (anyone can do it by simply asking Why? over-and-over again, or playing-the-opposites-game of negating every statement - for goodness sake four year olds do this all the time!) that it is deeply misleading to try and locate their origin.