Here's what I would say to Golbez to dissuade him from his invasion plan...

"Golbez! IT'S TIME TO STOP! What you are doing won't accomplish a Gods-damned thing! Think about it, man! If you invade the source and fill it with voidsent, what do you think is going to happen to the Source?!?! You will spoil the prize you want so damn badly! Geez!

Instead, calm your moon-ass down and let's negotiate. Remember how the lack of trust destroyed your world? You can probably see where I'm coming from with the futility argument then. But more to the point, I'm pretty sure that we could negotiate something where your people can come into our world and know peace and plenty. It just has to be done in a measured manner so as to maintain the Source's abundance. And part of that is trusting each other in the first place. So by abiding by our pact, you will make even more peace and plenty for your people rather than destroying it.

So just give up the Zeromus shit and let's actually solve the problems you set out to solve. 'No matter the foe', right? Even if it's your own stubborn hide? Yes I know it's anticlimactic, but we're talking about the lives of the people of both of our worlds, so suffice it to say I don't really give half a warthog ass. Come on, let's make something work here."