The Surfer's relationship with Galactus has always been complicated.
There are times when the two have been shown to genuinely respect each other. There have even been times of, not quite affection.
There is also the question of if it is really genocide. Genocide implies it is done with malice. Galactus only devours to survive. He is no more committing genocide then we would be if we ate all the cows on Earth.
I squashed a spider a few minutes ago, does that make me a murderer?
Is pneumonia a serial killer??
it is a concept that doesn't apply.
The Surfer has usually seemed to understand that, never condemning Galactus, but rather heralds who could lead him to other planets, but don't.
That having been said, the Surfer has always taken issue with Galactus not preferring uninhabited planets. In fact in issue #1 of volume 1, Lee tries to subtly imply that Earth may have been the first inhabited world Galactus came to.
Obviously that was proven false.
NOw, that is a complicated issue, but one thing is for sure, choosing to return Galactus to the devourer is out of character.
Any acceptance The Surfer had was based on the fact that Galactus simply is. He does what is his nature, and does it with out malice.
Changing him back is to alter a state that is more beneficial. it became, Galactus simply is... something better than he was.
I could understand this choice being made IF say the whole of life in the universe were threatened. That unleashing Galactus on unknown numbers of worlds would still be smaller in comparison.
I don't think this is that.
Yes but I think Surfer also understands that there are times Galactus needs to be reminded that he is a force of nature and not of malice.
Back in ish1 of the 90's series, he gains freedom from Earth and saves Nova who was captured by the Skrulls and Galactus then decides in anger to wipe out the skrulls one world at a time.
Surfer risks his newly gained freedom to remind Galactus of what he is supposed to be and Galactus agrees.
Galactus also at the time may have had feelings for Nova despite the fact he is supposed to be....Galactus.