You mean compared to the ghastly homophobia of comparing it to “immunity to LDH cholesterol: a persistent genetic “mistake” (i.e. the result of a copying error in DNA).” 
Regards,
Shodan
Thing is, of course, the argument doesn’t seek to ascribe the “yuk” factor of cancer to Teh Ghey. Rather, it relies on the “yuk” factor to alert the listener to the fact that argument X, advanced in support of Y, would also validate Z, Z being horribly undesirable (in contrast to X, which at least one side of the debate considers to be Perfectly All Right). And an argument that would validate something undesirable needs looking at.
F’rinstance, let some argument X validate Y, “less confiscatory tax laws”. Let it be logically established that X, taken literally, also validates Z, “child slavery”. No-one presumably equates less confiscatory tax laws with child slavery. But if argument X really would validate child slavery - which we all agree is horrifically undesirable - as well as less confiscatory tax laws, then it seems as though we had better toss out the argument, and instead advance some other, more discriminatory, argument W, which validates less confiscatory tax laws but cannot be shown to validate child slavery. Simple, really, and we need not at any time lambast our interlocutor for mentioning child slavery in the same breath as less confiscatory tax laws.
iamthewalrus:
It seems reasonable to suppose that religious laws restricting that which is “unclean” reflect a primitive understanding of the principle of hygene. One can imagine an entire village getting sick on a bad batch of shellfish, for example, and it’s easy enough to grasp the unhygenic implications of menstruating women. Likewise the Kosher rule that the same utensils not be used for both meat dishes and milk dishes could reflect the fact that semi-spoiled meat (which gets cooked thoroughly and is therfore safe to eat on its own) can contaminate the milk or cheese (which doesn’t).
It’s just people’s semi-vague understanding of what’s healthy.