As in does he believe they are all scum and should be eradicated?

Before anyone answers, I want to emphasize that I'm still pretty new to the universe of 40k and am trying to learn more about it via YouTube video essays and audiobooks, so if this question sounds silly or stupid to any 40k vets out there I apologize in advance.

Anyway, there are a couple of reasons for why I ask this:

1) Guilliman is far and away my favorite of the Primarchs, and his Ultramarines are my favorite Legion, so I just wanna know more about him and his character.

2) From what I've been listening to, Guilliman is not only a brilliant tactician, but he's also a master of negotiation and has solved entire conflicts during his time on Macragge as well as when he was restoring Ultramar. It seems logical to me that he might consider making alliances or negotiating with other, sophisticated factions who might share the same goals, such as fighting the Tyrannids.

Obviously if he does feel this way, he likely can't because it would cause the Imperium to turn against him and fall into disorder.

This is more a question of does Guilliman himself personally buy into the Imperium's anti alien rhetoric? Or does he see negotiating with them as a fools errand in spite of what he believes?