"Bruce killed all the villains in Earth-51 and Jason didn't like it, he's such a hypocrite."
A lot of Jason fans fall for this claim, but let's see what exactly is Jason's request regarding the subject:
Batman: Under The Hood
"[...] not talking about Cobblepot and Scarecrow or Clayface. Not Riddler or Dent..."
"Just him [Joker]."
"[...] because he took me away from you."
And there we have it. UTH was never about Bruce killing his adversaries after all, at that precise point it's not even about Bruce killing his adopted son's murderer. What Jason aims with his actions is to question Batman's methods, to confront his adoptive father on his inaction, and to ask for him to finally make a choice:
Batman: Under The Hood
You either let me kill my murderer, or you kill me. Choose which one's the hardest for you to live with.
Is that a reasonable request? That's subjective, and perhaps that's the point. He's a master strategist, trained, ruthless, cunning, the comic proves all of that explicitly; but he's still human, young, victim of murder, and someone's son. Even a master strategist is allowed to be unreasonable, to be emotionally raw, to be emotionally involved.
So what's wrong with Bruce from Earth-51? He did make a choice, but what was it? And what's Jason reaction?
Countdown To Final Crisis
"[...] I wasn't just taking revenge... I was going to war."
"[...] I've got friends up there! You think I'll just sit on my thumbs while they fight and die?"
"He [Earth-51 Bruce] couldn’t deal with my death and turned rogue. You just turned away."
For Jason, it's not about killing any and all villains.
What is it about then? Practicality.
It's not about giving up entirely on justice and people's rehabilitation and ressocialization, it's about being capable of putting a definitive end to the suffering and losses when they reach a certain unforgivable point. But commit no mistakes, nothing and no one gives Jason (or any other character for that matter) the "right" or "authority" to decide who gets to live and who gets to die. That's hardly a question that matters though. Nobody cares, just like nobody cares who gives Batman or any other superhero the "right"/"authority" to do what they do. Jason believes it needs to be done, and so he steps up, it's as simple as that.
That last line about Earth-51 Bruce turning rogue and our Bruce turning away, that's the crux of the matter that most people ignore. Jason doesn't want and never wanted Batman to become a rogue, a villain, a mere executioner. UTH is more than just Batman killing or not, it's about a son wanting justice served by his mentor, teacher and father, it's about a child wanting his unfair and cruel death to mean something to the only person it could've meant anything at that point.
Post-death Jason is, first and foremost, I would say, the Batman mythos' absolute judgment. The dead come alive to judge Batman's actions. He sees what was done for his victimhood using the Bat's MO, and he harshly disapproves of it. Points it out in a way no other character can quite manage because none of them are Bruce's adopted son, Bruce's family, Bruce's responsibility, that he let die, that he distrusted without proof (read: The Diplomat's Son and Consequences), that he marred the name of immediately after his death despite his biological mother using her dying breath to praise his goodness.
Jason is, secondly, I would also say, a counter-argument to Batman's methods. Everyone knows his limit, everyone can and do play with it, everyone knows he won't ever put a definitive stop to it, so what's the point? To make them afraid? They're not afraid. They know nothing he does will stop them forever.
So to conclude this needlessly long ass post (I love writing sorry), Jason isn't being a hypocrite for the simple fact that he himself doesn't want to kill all villains/rogues, doesn't see a need for that unless they step over the line (and yes, it's a nebulous, malleable line based on personal principles, which adds to the complexity (or perhaps mundane humanity) of the character). Not just that, but also because Earth-51 Bruce killing Joker wasn't about his love for Jason nor for justice, it's merely a symptom of his own mental instability (and your usual "Batman won't stop killing if he kills once" narrative that DC loves for some reason). Jason doesn't want that, he wants to matter. Most of all, he wants shit to change. Enough weak excuses against killing homicidal bastards. Enough making killing rogues about the heroes' feelings and/or lack of spine and not the suffering of the people vulnerable to their actions. He wants victims (himself included) to get their justice/revenge (and yeah, I think for him those two things can mingle and may just be one and the same in some cases).
Tl;dr: Earth-51 Bruce is sort of the opposite of our Bruce. Where our Bruce's sins lays in his inaction and ineffectiveness, Earth-51 Bruce's sins lays in his extremist actions and principles. Jason cares for neither, he cares for practicality and justice for the ones who are cruelly victimized like he was.
PS: This post is based on my own interpretation of the comics and the characters involved.














