And we might find more in common with some aliens than we do with our own species. Even if they came to eat us.
The idea that aliens might want to eat us is bizarre. I mean, even if we are sufficiently similar biochemically not to poison them outright, we are very unlikely to be palatable, and certainly not worth the enormous effort and expense of interstellar travel, just to get some food.
Of course, it's a scifi trope, but like the idea that Ming the Merciless might want to
marry Dale Arden it is simply a thinly-veiled racist exaggeration of the threat posed to "us" by "them", in a context where both us and them are humans.
I mean, humans will engage in beastiality, but even that is usually limited to mammalia, and rarely is
marriage considered. Beastiality across not just classes, phyla, or kingdoms, but between life forms from entirely different evolutionary histories is truly absurd.
As usual, it turns out that scifi is all about human relationships with each other, and has nothing to say about aliens at all. Scifi aliens are just an analogy for humans that the author doesn't want to explicitly name.