Ok, let's clarify something:

BAD LEADERS HARM THEIR NATIONS.

It is therefore perfectly ethical to wish for them to die.

Hell, it would be ethical to KILL them. We frown upon the latter for two reasons. Neither of them ethical, just pragmatic...

Reason 1: it's illegal.

Reason 2: it sets a bad precedent that ultimately harms a nation more than the bad leader does (as long as that leader is constrained by checks and balances).

In other words, all sides agree not to degenerate into assassinations, not because bad leaders don't DESERVE it, but because it would result in chaos. And in exchange, we are supposed to have checks and balances that keep any leader from doing too much.

However, that doesn't restrict us from HOPING that harm will befall bad leaders. Which would be good for the nation.

And bad leaders, like criminals, have placed themselves in an immoral position, and therefore have surrendered the right to be considered as having 'intrinsic value.'

I'm cool with killing criminals to stop them from doing their crimes (not as punishment once they're captured and rendered harmless, but stopping them 'in the act') for the same reason.