science

And yet, you’ll see many people posting elsewhere on social media that it shouldn’t be relevant.

Can’t imagine trying to share a life with someone who didn’t share my values, but there seems to be a contingent that think that other things should be more important.

No one is casting aspersions on the scientific method or the value of research

In your original comment, it seemed like you were questioning why the study was funded, then compared it to another obvious cause-effect about kicking a dog. Did I misunderstand?

the conclusion simply follows naturally from the hypothesis

The conclusion might have confirmed your personal hypothesis, but we don't assume that any conclusion "naturally follows" a hypothesis without measuring it.

The proposition here is that people who have opposing political views are more likely to be antagonistic to each other, that is a tautology.

The way you phrased it is a tautology, but the study didn't measure antagonism. It measured whether couples broke up or not.