But would it really be unacceptable for me to observe out loud that that was the state I was in?

That depends on what it contributes to the discussion. "I'm too tired to talk about this now" or "I find it distressing that you think a world with less stigma against infanticide would be fun" help us understand where the other is coming from, even if they don't help us understand the topic better.

"I wish you were dead" detracts from the discussion.

Can somebody else please give answering this a crack? Because I think I am too upset that this question is even disputed to be able to provide a clear answer. Best shot:

To me it seems obvious that there falls a category of Things You Shouldn't Say To People. "I wish you were dead" and it's variants definitely falls under that category. The utility you get from saying it is less than the disutility I get from hearing it. Also it leads to a poisonous society that no one wants to participate in.

Edit: I am amused that my post admitting to having an emotional reaction affect my reasoning abilities got downvoted.

Multiheaded said his/her (it's her, right? >_>) utility would increase, not happiness. If this is true, then, ignoring oppurtunity costs dead is what daenerys and other baby killing advocators ought be, subjectively-objectively for multiheaded.

edit: but it's almost definetely not true. Utility was probably being conflated with something, or Multiheaded was biased by emotional state (was REAL MAD, in less technical terms.)