So how exactly does this make the things Bernie proposes impossible? It merely means it will be difficult. And nobody thinks otherwise.
Just to reiterate, the point is that the New Deal and Great Society were not achieved by taking the no-compromise approach which, in this thread, you have repeatedly implied should have been taken with the ACA. Ira Katznelson's
Fear Itself demonstrates how, in order to get essential votes from segregationist Southern Democrats, FDR repeatedly accepted weaker versions of many of his programs, and also refused to support things like Robert Wagner's anti-lynching bill, to avoid losing Southern Democrats' support. He also made many other compromises, for instance remaining neutral in the 1934 California Governor's race, instead of supporting Democrat Upton Sinclair, in return for a pledge from Republican nominee and eventual Governor Frank Merriam that he would not oppose the New Deal.
Had FDR taken the approach to the New Deal reforms that you imply President Obama should have taken with the ACA, he would, for instance, have withdrawn his proposal for Social Security rather than pass it while excluding about half the labor force from the program, because including farm workers and domestic servants, both disproportionately African-American, would have offended the segregationists.