the little white girl comment was more of a humorous remark and not really the essence of my point

Okay, that's fair... bit of friendly fire on my part.

I just don't think the fact that something being scary and beyond our understanding is reason enough to eradicate an entire species without giving it careful thought. Wanting to kill what you don't understand is the heart of reactionary thinking.

Counterpoint, enough was understood by the characters in the story to identify a threat. I can agree that its ... knee jerk reactionary like somebody punching a person who jumped out from around a corner... but I'm less inclined to shove it into the political reactionary box.

Ultimately as a work of fiction the writer can come up with whatever justifications they want for why the aliens are bad and need to be mass murdered. Or why it's wrong to study and learn from them because only bad actors are doing it.

This feels like a good place to slap the "political reactionary" label for me. "Good guys need bad monsters to fight and overcome" makes for a pretty shallow story.

... something we don't understand and don't want to understand, the unknowable other.

I think you're wrong there in the bolded part. Cosmic horror isn't about people not wanting to understand something that is understandable because its inconvenient, its about seeing something that cannot be understood because its so different from human thoughts/wants/needs/desires that there is no way to even try to start comprehending it without destroying a human's psyche.