The Borg weren't in invasion mode, if they were then they'd have sent a real Borg armada to Earth in BOBW and kept at it later. They were in "Send one Cube down to investigate these fringe dudes" mode, "Scout" mode.
That they NEVER came in force shows they never considered the Alpha Quadranters a real invasion-worthy part of the Galaxy.
Unleashing their doomed-from-inception viral program on the Borg would've just made the Borg LAUNCH a real invasion.
Picard condemned nobody, you're just too much of a warmonger to think otherwise. You don't provoke a vastly superior enemy to move against you, you leave them be and let them just pass by and ignore you like the fringer you are.