"Dawn was supposed to be played younger." - Okay, Buffy was still the same age when Angel first saw her. Cope harder.
"Buffy was mature for her age." - What in the groomer justification.
"Spike was ALSO attracted to Buffy in s2 when she was underage."
JM said he played an attraction to Buffy as part of his character, correct. Whether you consider this canon confirmation or not, I don't care because --
Spike was *checks notes* a villain at this point. Remind me, what was Angel?
S2 Spike *checks notes again* didn't act on this attraction. He didn't start interacting with her like that until S4, again when he was still very much a villain (or at least demonstrably Not Being Portrayed as a Good Guy). Remind me, again, did Angel act on his attraction?
Spike didn't have a soul until S7. I can't remember, when Angel pursues Buffy, whom he canonically says he fell in love with when he first saw her (age 15 max), did he have a soul?
If you use any of these arguments to justify or downplay Angel's actions, congrats, you're an apologist.
The last one is, "Of course there are age gaps, it's vampire fiction!" And I will say this -- yes, I expect age gaps in vampire fiction. That's fine. That's a surface read. A deeper contextual read would be determining how those age gaps are presented and explored within the narrative itself.
Angel constantly uses his age and experience to both condescend to and make decisions for/about Buffy. He considers Giles a peer and Buffy a kid. He doesn't include her in any of the decisions that affect them as a couple until after he's arrived at a conclusion, then explains that he knows better in a way that completely dismisses her agency in her own life. Leaving Buffy WAS the best thing he could have done, sure, but the way he did it was extraordinarily condescending, to the point that Buffy started doubting her own heart and judgment. We don't see him treating Buffy as an equal until after they've been apart long enough for audiences to forget that this has never been their dynamic.
On the other hand, I can think of only one (ONE) time in the whole of the series run where Spike ever said, "I'm older than you," and it was in an effort to build her up, not tear her down or control her. Age gaps where the parties, regardless of age, treat and regard each other as equals? Oh no, the horror.
Age gaps where the age gap is expressly baked into the story in a way that supports the metaphor of "predatory older man preying on young girl" (you know, what Bangel was originally designed to be before they decided to keep DB around for reasons), yeah, I'mma call a groomer a groomer.
And you know what? I still support you if you know all this, accept it, but prefer Bangel to Spuffy. Because it is vampire fiction and I do not come to this fandom looking for uncomplicated, healthy relationship dynamics. In fiction, you can enjoy a lot of shit you would never condone in the real world. That's perfectly fine.
What I will argue against until I'm dead: pretending these Bangel dynamics do not exist, that Bangel is healthy, that Angel isn't a creep, that the actions of a souled "good" guy are 1-to-1 comparable with those of a unsouled bad guy, that this is just "vampire fiction" when the entire fucking show, especially in the early seasons, was monster-as-metaphor code for growing up. What other metaphor could Angel have been in S2?
TLDR: Anyone who makes a MORAL argument that Bangel is Better (which I know not everyone does, but god, do I see it ALL THE TIME) is full of shit. Also media illiterate. Maybe both. Probably both.