The Red Lion is probably so protective of Keith because he only had one other paladin before him. King Alfor. And we all saw how that went.
It’s funny when you guys point out how the Red Lion goes all motherly whenever Keith does something stupid and went from 0 to ALL IN with Keith real quick.
But like you guys DO realize that the last time the Red Lion had a paladin it ended horribly awful.
It wasn’t fully confirmed how King Alfor died we see him fall to his knees probably due to a fatal blow, but that battle... must have been terrible and painful and ugly and sad. I mean just look at what happened to Altea. How do you think Zarkon would act towards the person he personally blamed for the destruction of his planet?
Look at it from Red’s point of view. This guy makes you and you open your eyes and you instantly bond with him. (Kinda like Lance and Blue where it was effortless and instant and beautiful full trust.) So you trust him and you fight with him and you fly with him and for years he is yours.
The Lions have a bond to their paladins that we are just now starting to see in the new paladins. But you can’t tell me that the Lions can’t feel and sense what the paladins are feeling and thinking. We saw it when Red sensed Keith in danger. You can’t tell me they’re not clued into what the other Lions are feeling and thinking (even if slightly) and by default their paladins. I mean these Lions care so much and are so damn attached to their paladins, and they protect them and the people around them. You remember that one time Green protected Shiro and Pidge or Yellow protecting Lance and Blue and I could go on.
And then something terrible happens.
I mean this guy, Zarkon, has stood by them for years; and they all admired and listened to him because he was their leader and friend and they cared about him. They protected him and helped him out probably at hundreds of points. All of them not just Black. Right now the Lions are helping the paladins as much as they can and showing them cool stuff.
But back then the paladins and Lions were discovering things together. They were making their way through things together discovering unknown things at the same time. And then this guy starts to display these dark feelings and gets violent and turns right out evil and they must have felt so damn betrayed and hurt.
Believe me, it must have been so heartbreaking for Black (the whole: My paladin is going crazy, oh no he died, oh he’s alive, oh... he’s evil.) but was not bad for just Black. It was heartbreaking for all of them. But Red must have been the second most affected because he’s the right-hand man and because of his bond to Alfor, Red must have felt affection for Zarkon too. Zarkon it seems was Alfor’s best friend. That’s some deep stuff.
And then the other paladins get killed. He has to live through the feeling of the lost connection to them, the broken bond. Red has to feel the pain of the other Lions through his connection to them. Red feels all of this and has to remain strong, a leader in the absence of their leader. He has to support Alfor.
Alfor sent the Lions away, presumably after the fall of the other paladins. They were all probably so hurt, ALL OF THEM, had JUST lost their paladins except Red, so they all had to be sent AWAY FROM EACH OTHER while they were all completely and UTTERLY HEARTBROKEN. Mourning.
And Red had to see all his friends get sent away, without knowing when he'd see them again. To top it all off, Alfor stays after sending Allura away, so Alfor probably knew there was going to be a show-down and some part of him knew he was gonna die with all the prep he did to keep the other Lions and his daughter safe. Red had to feel that, sense that. Red had to see all this through his bond to Alfor even when he couldn’t be with him. Betrayal. Fear. Hurt. Desperate Blind Panic. Sadness. Nostalgia. Anger. Regret. All of it. Red had to feel it all but he couldn't do ANYTHING. HE COULD DO NOTHING AT ALL TO PROTECT HIS PALADIN.
And the cherry on top is when it's over... When he's watched King Alfor fall from King Alfor’s own point of view... When it all comes to a bitter utterly disgusting end... He gets captured. He gets captured by the very people who cause so much pain and hurt and sheer panic. I'm surprised Red didn't have an alien breakdown. We aren’t told when he gets captured but it was too soon no matter how much time had gone by.
Instead he shielded himself and locked everyone out. Even when 10000 years go by he doesn't forget Alfor.
So then this scrawny kid comes trying to make him open up and of course not. F you kid. And I’m sure Red knew about the part Galra thing and that was one more reason to NOT OPEN UP. But then he looks again at this kid who has a fire within. Who ISN'T his King. This kid who isn't Red's King Alfor.
But in those few moments reminds him so much of his lost friend. And he knew about the half Galra thing and he saw hope that not all Galra are the same that they've been for the last 10000 years. This kid isn't his King but he could be. In his own way, he could grow to be, not exactly like King Alfor, but similar to King Alfor.
And then this kid goes and gets himself thrown out into space and Red just can't see him die. So he opens up and saves him because he couldn't do it for Alfor but he will protect this stupid kid or he'll DIE trying.
Because this kid is his. And soon he'll be this kid’s
Anyway... Sorry for the long post.