My thought process has always been that the Arbiter is "bad news" in the End Game.
There's the Pure Route where you actively "avoid" your monster side i.e lack of Corruption. Then there's the Corrupt Route where you actively purse your monster side i.e high Corruption.
I see the Arbiter as a higher force, something the human mind isn't designed to handle. So when it takes you over you sort of become "one" with it; losing your own "self" in the process. Some may like that, others...not so much, especially if you're trying to defend your friends. I mean there's the conversation you have with Mia for example; you sort of laugh about murdering her best friend IN FRONT of her, and we as the player, have NO control over it.
All the Arbiter's requirements have also been a hit list, so I'm just prone to believing THAT is why it wants us to do that before we obtain it's power; so that becomes Corrupt enough to handle his mindset without resistance.
Some things to consider:
1) The Eye doesn't seem to have any preference. If you have high corruption it urges you to consume. If you have low corruption, the script seems to suggest that it urges you to find allies. When it asks you why you fight and what you want out of your power, it doesn't provide it's own opinion but it's a very reasonable conversationalist. While we can't confirm what the Eye says in low corruption routes, I don't think it's correct to assume it's the same as in high corruption.
2) When MC consumes superhumans, he usually has to mentally fight with the invading consciousness. This is especially prevalent when he tries to consume Danica where the implication is that it's possible to lose his body. In fact there is a fairly significant amount of exposition in this particular scene, allowing a possibility to have more than one consciousness inside a "vessel".
3) If corruption makes MC selfish, bloodthirsty and more likely to consume, why would he even want to lose his sense of self. It makes more sense for such a character to want to overpower and consume rather than being ok with merging with some alien consciousness and losing part of himself.
4) From a meta perspective, there are 4 different "outcomes" in the discussion during the third evolution. Selifsh + Power, Selfless + Power, Selfish + Love, Selfless + Love. The Eye actively rejects the third option, claiming that "the g.. fate is linear anyway". The selfish/selfless attribute is tied to a morality variable, while the power/love isn't tracked at all. So if I had to guess, the important part is the morality. You can actually have high morallity with high corruption. I have a playthrough with high corruption, Danica and Jake consumed, and 14 morallity. Morallity starts at 10 and at this point in the game you can have anywhere from 6 to 15.
5) MC doesn't necessarily need high corruption to understand monsters. His memory powers do the job for him. He may not be able to understand the language, but does that really matter when he has the capacity to understand them in such a "hollistic" manner? This innate understanding improves with evolutions, not with the corruption stat.
6) Lastly, in my personal opinion, merging with the Eye is an inevitability. Even if we assume that MC is the strongest superhuman in the world, it's unlikely that he will become the "supreme being" (as foreshadowed in a Nico deadend) by himself. I think that the circumstances will force him to merge with the Eye, which will be the only way to connect to the "higher plane" and the ending result will depend on the player's wishes. For example:
1) Low corruption - MC will stop a monster invasion and live a happily ever after with his harem.
2) High corruption - MC will stop a monster invasion and go on traveling the cosmos and reshaping it as he sees fit.
3) High corruption - MC will try to create a new world where monsters and humans coexist or even merge to create a new species.
Something like that.
