That is an opinion, sure. Another is that you stop separating 'The StAtE' from 'The People,' because it decent societies there is no effective difference. (Actually in all societies, there is zero difference whatsoever, but we really aren't here to talk about implied consent)

The state doesn't need to be infallible, because people aren't. But we can be sure beyond a reasonable doubt. If a mayor of a province that has directly harmed hundreds of thousands of people and was found with literally 40 tons of Gold and Cash says they're innocent, they have a pretty large hill to climb. We can be reasonably sure he at least had something to do with the bribes, and we can be reasonably sure a poor student from a poor family turned extremely low level politician did not find a way to hoard 40 tons of gold and cash through legitimate means. On its face just that evidence pushes that beyond a reasonable doubt, but beyond that the offender still gets a guaranteed defense in court. The one referenced obvious lost, because of course he couldn't defend those actions or explain away 40 tons of gold and cash, but he had the chance to push some, ANY doubt into the mind of the jury.

This also isn't like the US, evidence can't be thrown out of court and doesn't have to be approved by the court; meaning any exculpatory evidence the defense can find can and does get introduced. If you're innocent and can prove it in any way, congrats. If you find a filing mistake by the People's Prosecution, congrats. If you can prove a flaw in their methodology, congrats. 'The State' doesn't set the narrative, the court only exists as a way to to guide the jury on what the law is. It has no relationship with the prosecution.

And yes, the death penalty is reserved for those that cannot be rehabilitated. A man does not come back from literally decades of taking bribes. A man cannot change that drastically overnight, it is pure naivety to think otherwise (and ignorance of psychology). The Norway style of keeping mass murderers alive forever just to... say that they didn't kill them and feel smug about it does nothing for public safety, and just costs money. All for a smug since of superiority about being kind to people that want to kill you. China was under a dictatorship less than a century ago, they had this whole big revolution about recognizing and not being kind to those people.

Mass murder is not what's happening; but your world view is quite common and naive among young aspiring liberals wanting to ignore the violence inherent in your very existence.

You are not unique for wanting incremental peaceful changes. Everyone goes through that phase. Then you start reading history, and theory. Or worse, you actually try to put your ideals into practice and are met with violence that you don't realize your ideals cannot overcome.

If the world were sunshine and rainbows and not ruled over by pedophiles that literally eat children and flagrantly kill anyone who's a threat to their power your ideal would be great. Fantastic even. But your ideal is not one born of education or experience. It is born from the lack thereof.

In the real world, the one in which we live, the one in which you know someone (1 in 4 in the US) who has been a victim of Police Violence, the one in which you have met someone (1 in 3 globally) has been a victim of the US Military Industrial Empire, the one in which the leaders of the 'democratic peaceful free world' are literally all pedophiliac cannibals, the one in which literally every aspect of your privileged little life comes at the direct cost of a child in Africa or South America or India suffering, violence has to happen.

If we really want to delve into Theory, violence is inherent in the concept of society. Restraining someone is violence, it is a violent act. It is the least violent act that can be taken when they do not agree with your imposed social contract of sunshine and puppies, but it is still violence.

There is no possible way to get to a world without violence, without instituting a hive mind (i.e. eliminating society), Eugenics, or otherwise magically curing the human condition itself. Every possible society will have some violence, because there will always in any evolving society be those that go against what the current Social Contract is. Always. Sometimes for good, sometimes for evil, but there will never be a world where everyone is content — mainly because contentedness means stagnation and we are unlikely to ever be 'fully' socially evolved as to call for stagnation. There will always be better to strive for;

But that evolution cannot happen if those with the power and all the capability for violence intentionally stop progress because it hurts their personal progress towards being wealthy. It cannot happen if, with every breath and step we must keep handling those that are against the concept of society with kids' gloves and pretending they can ever change.

All current science points to the existence of those whom physically cannot understand empathy. They lack the parts of their brain that allow for that. And without empathy, there cannot be society, much less a violence-free society that you and every other real human so desperately wants.

Since Eugenics is bad, and since Mass Murder is bad; that leaves us with the current system — when those with this defect show they have no self control and abuse this defect of theirs to harm the rest of society, we put them down. Education cannot work; and they have nothing in their head stopping them from lying about being rehabilitated, and we have no such technology (and never should) to read minds and figure out if they're being honest. So the only safe route for all of us, all the real people with empathy to live, is for those that cannot even fake being one of us to die.

The alternative is human history, and one really doesn't need to look far in human history to understand why we cannot have repeat episodes.