I could point a gun to your head and ask you to explain why I shouldn't pull the trigger.

That scenario doesn't lead to discovering the truth. If I deceive you with bullshit and you don't pull the trigger, that's a victory for me. I invite you to try again, but next time pick an example where the participants are incentivised to make true statements.

ETA: ...unless the truth we care about is just which flavors of bullshit will persuade you not to pull the trigger. If that's what you mean by morality, you probably agree with me that it is just social signaling.