Out of all of them, apart from Allura, Shiro probably deserve to be angry at Keith for being (half) Galra. Imagine all those tortures or made for entertainment he and the other prisoners were. They are the reason his life was ruined (cos I am pretty sure he would have many success when he returns). But no, he didn't blame Keith at all for being one like Allura did. He supported him, gave him a hug while we also see Hunk actually being negative of him during their mission. Just. Bless Shiro fam!!
Yes, yes!!! Out of everyone, Shiro was Keith’s anchor through it all. He’s the one who checks in with Keith and notices that something’s wrong; he’s the one who sees him through the trial and offers nothing but unconditional support after the reveal. Shiro was there for Keith in a way no one else ever was, and I wish that fanon didn’t just gloss over that so much.
Shiro’s easy acceptance is definitely do to their close bond–“My life would be a lot different without you,” Shiro being the one thing who “can really calm Keith down,” Shiro being the one Keith “desperately wants to see,” ect. But I also think Shiro’s able to empathize with him more because he understands a bit of what he’s going through. Keith’s galra arc parallels Shiro’s own character development in a lot of ways; both of them struggle with this notion that they’re irredeemable, that they belong to the galra empire. When Shiro looks at himself, sees what the galra have done to him, he sees a monster
But when Shiro sees Keith is galra? His gaze softens. His eyes go wide in wonder, like he’s really seeing Keith for the first time. And his expression doesn’t evoke a sense of fear or rage here; Shiro stares on in awe, completely mesmerized. His body language and the lighting of the scene both feel open and calming–serene, ethereal. There’s something about the luxite’s glow that’s reminiscent of Allura’s healing magic. It’s a power that’s portrayed here as good, just, and benevolent. For Shiro, I think in a way this is healing–he’s allowing himself to let go of his hatred for the galra (a process we already see begin with Ulaz) and this notion that being “part of the empire” makes him broken and corrupt. He’s also coming to terms with Keith’s identity, an identity that Shiro accepts wholeheartedly.
Shiro hates himself for his ties to the galra, but he’s able to love and support Keith despite that. And if he can still see the good in Keith, then he knows there’s still hope for him. I think that, by accepting Keith, he was kind of able to come to terms with some of his own trauma, and be more forgiving of himself as well. And it certainly helps that Shiro realizes Keith still cares for him too–still treasures him as his closest person after all this time, the one friend he desperately wants to see. I think it really meant a lot to Shiro that someone adored him so much, that they still loved him despite the year apart and all that’s changed. Because their mutual love and support definitely goes both ways.
And I was just talking about this before, but one of the most prominent themes in fanon was always “X character is the first to find out Keith is freaking out over being galra, so they help him through it and offer wholehearted comfort and support. They fall in love, ect.” Always, this role was a position delegated to Keith’s chosen love interest. So I find it very interesting that Shiro, the one who actually fulfills this role in canon, hardly ever seems to get credit for it.
And in those aus, I often saw Shiro relegated to the role of the Betrayed Friend. The one who couldn’t bear to look Keith in the eye anymore, who took his reveal the hardest and refused to even talk to him. Which always sounded incredibly out of character to me, and I’m so glad canon proved that it was. And I will never understand the fact that fanon often limits or overwrites Shiro’s role in Keith’s galra arc simply because they’d rather substitute him with their fav. This idea of Keith having an anchor during his galra reveal was just so romanticized in fandom; I feel like the fact that that person ended up being Shiro should at least count for something. I mean, when Keith left for his mission no one else would even say goodbye, but Shiro is right by his side