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.