ORIGINAL: Sabin Stargem
I would like to send a fruit basket to independent worlds, with a note reading: "Please join me, here is a small fraction of my wealth. Think about it."
I know.. I mean, its kinda logical too.
Even irl =D
Imagine if suddenly a vast galactic civilization spanning hundreds of colonies revealed themselves to us, not to mention that they also were friggin human!
Now, what do you think Earth as a whole would do when faced with 2 choises?
1. Die, get invaded.
2. Join this incredibly large powerful empire OF OUR OWN KIND, and reap the benefits in near-immortality, end of famine and disease, and being able to see the universe via their space tourism as being part of their empire.
Honestly, no independent world would reasonably say no

Its understandable when it comes to alien races like nasty insects or whatever, but there should really be a diplomatic "join us?" option for the same race, without having to send a colony ship.