What I keep thinking about is that we are all... Humans. Like, the same animal, same way of thinking etc. And yet our answer so many times is conflict.

The only reason conquerors didn't kill all the conquered was for taxes and slaves and so on. Imagine if resources were not an issue ( advanced enough tech) and you wanted to avoid confrontation.

Sending a near light speed bullet to explode a star seems a good trade-off to keep your dominance.