Jason doesn't think killing is objectively right. He knows what it does, and the consequences of it.
But compared to Batman's no- kill rule? It's a whole lot better and more effective.
It won't last long-term, but it's still enough to get rid of criminals who are the worse of the worst. Criminals who, despite given chance after chance, do nothing to change, do nothing to atone, and carry on torturing or murdering hundreds if not thousands of civilians.
So sue Jason if he thinks killing heinous people isn't bad. But you cannot say to him that throwing them into a revolving door and expecting them to change will do anything.
Batman's doing this for vigilantes shit for, what? 10+ years? If his methods actually worked, than why isn't Gotham better?
Oh, because he doesn't tackle the root of crime. He doesn't try hard enough to prevent or reduce the causes for why people to turn to crime, focusing on beating up blue-collar criminals and not white-collar criminals or corporates who continuously get away with crime/harm.
It's honestly very simple why some people resort to crime. Lower class criminals become criminals for survival, or to support their worse off family.
For drugs, people tend to buy them due to bordem, peer pressure, for pleasure, all sorts of reason. But the thing is, having a support network is crucial, because then, they may be less likely to try drugs in the first place, and if not, a support network may help them to quit. Plus, by decriminalising, or legalising drugs, you can regulating it, put rules in place to reduce harm. The quality would be good, it's possible to limit how much someone gets, and it can help prevent kids from becoming addicted and turning into a druggie in their later life.
Another things is employment and education. A lot of lower-class criminals resort to crime because they can't get a legal job due to their past or due to not being educated enough and have to resort to crime to get by. So buy creating a job that allows them to be employed is crucial.
These are only a few things that cause someone to commit crimes.
And yet not enough has been done to tackle this problem, and because of that, the least Jason can do is rid the streets of criminals that are only commuting crime for the sake of it, feeling no remorse for their actions.
So yeah, Jason doesn't think killing is completely right or morally wrong, but it's a necessity he's willing to take until he can tackle the root cause of crime. Cause he sure as hell knows Bruce and Batman sure isn't doing enough to make any meaningful changes to Gotham.
