What's the alternative to rationally debating ideas that violate our moral sensibilities, assuming some people hold them?

Is it to declare with 100% certainty that any idea that violates our moral sensibilities is false? Is it to say that maybe there's a small chance that ideas violating our moral sensibilities are true, but even so we must never discuss them so if they're true we're out of luck and will never reach that true belief? Is it to say we may discuss them, but not rationally - that is, we must let the screaming protesters into the debate so that they can throw eggs and mud onto the debaters because that will improve the quality of discourse?

Also, I bet (and correct me if I'm wrong) that whatever debate you've watched was not about "Let's round up the [Other Folk] and execute them." My guess is it was either about allowing them voluntary euthanasia, allowing abortion or infanticide on the part of their parents, or ceasing to specifically allocate scarce health resources to them.

That means that what we're really talking about is "Any idea that can be massaged into sounding like an idea that violates our moral sensibilities is 100% certainly wrong, or should never be discussed, or needs more egg-throwing."