Weird I'm not seeing any links to metaethics, semniotics or ontology. Is that because you fundamentally don't understand the topic?
Let's pop that hubristic little bubble of yours.
If fetuses are infact little clumps of cells, then how do we differentiate them from other little clumps of cells? Clearly there must be some additional property that lets us differentiate them, and if an additional property exists then it has a possibility of moral relevance. In other words, the mere fact that we can distinguish fetal tissue from other tissue means that we can ascribe moral value, rendering your assertion that it must be morally equal false. Even more dumbed down for you, if A does not equal B then Moral value of A does not have to equal the moral value of B.
So completely contrary to your claim, the reasoning does not actually follow, because fetuses and cancer cells can be easily determined to be different and ascribed different moral value.
Edit: Oh my science! I accidentally steel-manned you. I'm so sorry. You're not saying that fetuses are inherently morally equal to cancer cells, you are saying that self-awareness is the criteria for moral worth (it's not) and that ascribing moral value to a fetus requires asserting that it is self-aware. Possibly even stupider than denying classification theory.