I say it's objective because there are certain traits which one would fairly reasonably associate with being a good leader.
I know what you're saying. Really, I do. However, it is my opinion that you've fallen into the trap of mistaking things that are eminently reasonable
to you for things that hold universally. There are people out there who hold the opposite views to you, and they're not a small fringe, either. To some, for example, personality is more important than policy, because leaders also perform a representative role. It's one of the things that gave Reagan an edge.
So, no, it's not objective, regardless of how obvious it seems to you and me.
Well. I don't think there are many objectively good or bad policies.
That's why I slapped it in between quotation marks. It's as "objective" as your view on who makes a better leader. In other words, not at all.
Without wishing to go all Godwin's Law, I don't think there's any party extreme enough to have "exterminate the Jews" as a policy
Maybe not today (and even then, I'm not sure that's the case), but you're proposing a replacement for
democracy. It's only been 100 years since NSDAP's rise to power. Maybe it won't be anti-semitism next time, but terrible views gain prominence all the time.
Finally, c'mon. Work with me at least a tiny bit. I asked you to pick a terrible view and imagine people are voting for it. Decide for yourself what the worst possible outcome is. If you just say "no", we can't really look at how robust your proposal is.