Let me put on my psychology goggles
Frankly, I don't understand what's wrong with the skull. And I could also see why someone would hate the skull. The alien is a metaphor monster, so if someone thinks the skull is spooky, they're probably afraid of skulls in the context of sex. If someone isn't, and they think a featureless dome is scary during sex, they're probably a repressed homosexual.
Can we at least agree on this