R. Star wrote:
Well, given the alternative was the destruction of our Galaxy...
Hate to tell it to you, but Voyager provoked them just as much as the Borg. Their first encounter with 8472 was them barging onto one of their ships as if they had every right to be there. Then they tried tractoring it, and beaming it away.
Their next encounter with Voyager, they're obviously collaborating with the enemy that invaded them. It's only then the "your galaxy will be purged" bit came. Which is a dubious and vague comment. Then they invade their realm... using weapons of mass destruction based on Borg technology. That's when they decided to target the Federation. And if they're all that evil, why was Janeway able to talk them down easy enough? They probably would've stopped at the Borg and gone back to swimming in their green goo absent Voyager.
Exploring a mysterious ship when you don't bother trying to communicate yourself doesn't justify you saying you're going to destroy the Universe. If you do that, and prove you're more than willing to be hostile, then you shouldn't be surprised when these guys you threatened decide to take the fight to you.
Yeah, the 8472 turned out to be reasonable but that wasn't til long after they'd given off the impression they were Xenocidal maniacs.