I've slowly reached the conclusion, that in the case of Marxism, it is not trying to prove "strong atheism", but rather the intellectual premises of a particular worldview which is by definition atheist. it therefore involves a positive assertion about the nature of reality which has the implication that god is excluded from the realm of possibility. In this instance, Atheism is not a "stand alone" position which can be treated as a hypothesis subject to proof, but a conclusion logically derived from accepting the premises of a dialectical materialist worldview.
Atheism appears too heavily connected with a theory of knowledge to be tested as a knowledge cliam in itself. Materialism is taken to be self-evident if a person accepts the reliability of sense-perception and therefore the existence of the objective world. The belief in the reliability of sense-perception and the objectivity of the world therefore makes it a "scientific" worldview.
The only aspect of this which could be subject to some level of proof is the cliam that Consciousness exists only as a product of the brain and cannot therefore exist seperately from it, but this is also intricately linked to a form of philosophical reasoning rather than being a scientific hypothesis. If consciousness always derived from nature, there cannot therefore be a supernatural force "behind", "beyond" or "above" and as such, religion is considered an illusion. Marxism is therefore a form of Metaphysical naturalism.
The conflict between weak and strong atheism is probably be a conflict between
Methological Naturalism (in weak atheism) and
Metaphysical naturalism (in strong atheism) as different ways of approaching knowledge and defining existence. Metholodical Naturalism is a way of aquiring knowledge through science, whereas Metaphysical Naturalism is a position that only natural elements exist. The former cannot bey definition rule out the existence of god because it is only a method of establishing disbelief, whereas the latter can and does because it is a philosophical system of beliefs about what exists.