They don't discuss lobsters, they use the tongue-in-cheek remark "God is a Lobster" in beginning to talk about how the object called "God" performs its functions according to a "double-pincer" movement. It brings other objects into formation, as does the human mind, but it adds the second step of completing the formation so that those other objects appear to be a priori permanent and unchangeable. (Later on he and Guattari use the image of geological processes, and the difference/relation between the sedimentation process and sedimentary rock.)

In other words, "God" is an object through which we postulate more than our minds can actually know, in order fix our system of judgments about the world. The "God" Deleuze critically talks about is an apparatus of capture, a feature of human power/knowledge relations, and a very dangerous thing indeed.

On the one hand, this meme lowkey smears my guy on some guilt by tenuous association ... but on the other hand, if it leads even one JBP boi to read Deleuze and accidentally learn something, I guess it's not all bad.