Curate, connect, and discover
In the first scene, Aziraphale tries very hard to convince the other angels that Crowley is an enemy. It doesn't work for all of them because Michael grows suspicious, but the others seem fairly convinced, he's telling the truth.
In the second scene, Aziraphale tries to convince Crowley that the Metatron is a good guy. The phrasing he uses is similar as in the first scene, and so is his tone of voice.
I think it's possible that at this point of the story Aziraphale already feels or even understands that the Metatron is not a good guy, but he either tries to convince himself that this feeling is wrong or he tries to keep up appearances.
Of course, it's entirely possible that the similarity between both scenes is a coincidence, but in GO there are so many hidden clues between the lines that there might be some significance to it.
"Nah, he's not monstrous, that's utterly ridiculous. He always puts other people's happiness before his own. He doesn't even permit himself to dance with me unless he plans a Jane Austen ball (she has balls) for other people's happiness first.
No, he never was abusive. He was supportive whenever he could and sometimes even, when it would have been the smarter thing to keep his mouth shut.
But, yes, he's a prick. Throwing away everything we could've had, just because he thinks, he can do goody-good in heaven.
They'll roast him alive.
Which they tried to do before."
Fandom acting like Aziraphale is the Bad Guy for asking Crowley to become an angel again is something else. I'm not arguing that offering to turn him into an angel again was the right thing to do, but CONTEXT MATTERS!!
Things Crowley has canonically said about his fall:
"I never asked to be a demon. I was just minding my own business one day and then… Oh, lookie here, it’s Lucifer and the guys. Oh, hey, the food hadn’t been that good lately. I didn’t have anything on for the rest of that afternoon. Next thing, I’m doing a million-light-year freestyle dive into a pool of boiling sulphur." (Aziraphale appeared to Crowley right after he said this so it's not outside of the realm of possibility that he found Crowley by following his voice in the first place.)
"I didn't mean to fall. I just hung around the wrong people."
"I didn't really fall. I just, you know, sauntered vaguely downwards." (Crowley says this to Aziraphale in the same scene he asks for holy water.)
Crowley was turned into a demon against his will.
Crowley hates being a demon too. It makes sense that Aziraphale would mistakenly believe that Crowley might accept the idea of becoming an angel again if what we were witnessing was Aziraphale being honest with Crowley in the final fifteen.
Again, I'm not saying he was right to ask that of Crowley, but let's not just decide that Aziraphale is a Bad Person for asking when he's witnessed ways in which Crowley has suffered as a demon.
There is indeed a lesson to be learned here, but why bring a little more context into the situation when it's just easier to villainize Aziraphale, am I right?
Yes, he was wrong to ask Crowley to become an angel again because it's not what Crowley wants. No, he's not a monster for offering. This is seriously all because of their stunning inability to communicate what it is they actually want.
Aziraphale has to break free from whatever hold Heaven still has on him, but he doesn't deserve to be treated like the Bad Guy.
It is entirely possible to criticize Aziraphale's actions without painting him as a monstrous abusive prick.