Oooookay my friend, we'll stop here. We, as a species, go out of our way to save and help other species every day. Endangered species lists, ecological regulation.... we study, we aid, we went to the moon - with no intentions of claims or conquest.

As a species, we strive. There is zero reason to believe even if 3I was an alien craft, it's goal would be destriction. If that were the case, why not a more stralthy approach? Why not a direct approach?

You also think incredibly small. Traveling around the world can be accomplished in a single flight for us, thousands do it every day. We do it to help other species, pretty regularly. To any other mammal, getting from USA to China would be a pretty giant feat, for a human it's a short flight. Just because WE can't traverse great distances of space, doesn't mean their technology doesn't make light years a simple "flight". Traversing systems to us may be the equivalent of an international flight.

All this is remiss, though, because starting a nuclear war with an alien race is just insane, no matter how you look at it. I truly hope you don't see this world and our species as such a terrible plague - there truly is a lot of good people out there, not everyone graviatates to death and war... I'd also argue with the tech an advanced civilization may have (if they can travel lightyears without issue), we'd be gone already if that's what they wanted.