I.e. I assume if some madman suggested killing every second child in Athens to appease the gods, nobody would seriously even discuss it and nobody would vote in assembly.

So where was the line? Wikipedia says, with no sources, that

In the 5th century at least there were scarcely any limits on the power exercised by the assembly. If the assembly broke the law, the only thing that might happen is that it would punish those who had made the proposal that it had agreed to.

I asked this question about a year ago and got no answers, so I am trying again. Sorry if I worded it wrong, English is not my mother tongue and I might not know some terms.