Well, I don't consider Greenwald to be a liberal, but otherwise I agree with the general sentiment of the article.
To really address wealth inequality, we need to make labor scarcer, and we can only do that by reducing immigration.
I also think that immigration probably hurts liberalism, at least in the medium-term. It's not a coincidence that the two largest expansions of government (New Deal and Great Society) happened during the
period when the foreign-born population was relatively low (between the Immigration Act of 1924 and the period when the effects of the Immigration and Nationality Act of 1965 began to be felt). It's a lot harder to add new government programs when conservatives can portray them as hand-outs to non-whites.