Lucifer does have reasons to not trust alastor which is fair especially because of his deal with Charlie but I think Lucifer has a bias towards sinners and we don’t know how much his pov has changed. Alastor also has reasons to not like Lucifer which is probably rooted by Trauma.
Lucifer 100% has a bias to dislike Sinners! He considers them a disappointment canonically. "They got gifted free will and look what they did with it!" "It doesn't matter how well-intentioned you are, they're always going to disappoint you."
So many people in this fandom forget that Lucifer don't give a shit about sinners. He got hellborn immunity from Exterminations, but gladly throw sinners away like nothing. It's CLEAR that Luci hates them and sees them as failures. I just wish the fandom wouldn't gloss over it all the time...
Also technically hellborns were bron there so exterminating them for no reason is really unfair. Luci believes that its their own fault if they are here.
Yes and I hope this is an arc he will go through, learning that not all sinners are the same.