Is Existentialism an Eliminativism?

Partisan formation around the old "Continental-Analytic" split (now completely passe, it seems to me) reified over the years into a view of things where, broadly speaking, existentialism was a part of the philosophic "left" and particularly represented a defense of the freedom of the individual. In its most debased form this interpretation placed existentialism as a kind of refutation of Newtonian determinism. Reading Sartre in Contemporary Philosophy this semester, this seems to me all wrong. I think that Sartre is a kind of eliminativist about the self, certainly he is about any classical, Platonic/Christian concept of a transcendent self (he's explicit about that), but his whole theory rests on the idea of consciousness as a no-thing, the negation that emerges in dialectic with the material world. "I am not that," is Sartre's Cogito. He wants to be a materialist, and maybe even a reductive one. Isn't Marxist dialectic (an uppermost concern of Sartre's) a sort of reductive materialism? There is nothing beyond the physical state of affairs; that is the ground of all of the rest of being. "Existence precedes essence" points ultimately to Hume's psychology. When I did a Kant seminar a few years ago and we read the first Critique, it struck me that all of Sartre was already there in Kant (not an idiosyncratic stance by the way). Take away transcendental rationalism (as Sartre, at least programmatically, certainly aims to do) and you get...Hume. Or maybe Sartre is Berkeley! Kant hated it when people said that he was Berkeley, but they did say so at the time.