I don't think Sanders people would consider themselves "liberal". I know I don't.

It's important to understand that while the Right in America uses “liberal” to encompass everything to their left, the American Left (in line with much of the world outside the US, which did so longer) tends to use it specifically for a center-to-center-right pro-capitalist position roughly coextensive with neoliberalism; the (decreasingly, but still) dominant centrist wing of the Democratic Party is “liberal”, but not, in that view, most of the rest of the Party.

Indeed. Liberalism is the ideology according to which negative rights prime over everything, the rights to property are the most important, and freedom of association is paramount.

Leftism emerged as sociology critiqued the idealist liberal notions for their ignorance of real-word effects due to material reality on the actual freedom and oppressive social structures that strict classical liberalism creates.

That seems accurate. Also, neo-liberalism emerged from economics with an imperialism backdrop. It's the philosophy of globalism.