I never really understood things like this. The reason we get squicked out by stuff is because it's human or reminds us of human. We're often disgusted by cellular tissue leaking out fluid when it's something like meat exuding blood or mucus, but not a grapefruit dripping juice.
Depending on context, sex can be exciting or disgusting when it's between other people like us, but when paramecia or bacteria exchange genes the images is mostly clinical. What's wrong with this alien that it has such human-like feelings about our parts and fluids?