Australia

I'm personally not taking the petition seriously, I assumed it's more of a statement of their hypocrisy. Like you said, it's not appropriate and not a substitute for justice. Lock them up in isolation for a serious stretch of time along with the other violent domestic terrorism participants.

And one thing you touched on, I'll note that there is an unfortunate tendency (at least online) of people proclaiming conditional rights, like the US Democrat voters saying they hope Republican-voting immigrants get deported, or nominally progressive people misgendering others over political disagreements because 'they deserve it' or because it's an easy attack. Really shows their hand when their convictions are conditional. Either you believe in a right or you don't, be honest about it.

As for NZ... they've already had too many of our nazi scum over there.

Additionally, is there really anything to be gained by getting rid of this one guy? Some other asshole will emerge to take up his role.

On one hand, you're correct that removing a leader doesn't solve the rest of the problem. "If you could go back in time and kill Hitler", the Nazi Party still would have certainly gained major ground.

On the other hand, I recall one of the times Sewer went to prison, there was a power struggle and drama. So it probably won't hurt.