I just found out why it matters when a leader pops up and says "Are you preparing to attack me?" or other such things where there are two options -- one truthful and one not-so-honest (if you really mean harm).
I betrayed the Babylonians when they suspected my units were amassing on his border, and said "Don't worry, just passing through"...move along, nothing to see here! LOL Anyway, a few turns later when he went to war with a city-state I liked I declared war on him. Babylon said I have betrayed my word in telling him I wasn't going after him, and he would make sure the world knew it.
My diplo relations appear to be lessened with other civs (but not city-states). So, that is why you may want to tell the truth to your opponent -- if he catches you in a lie, all other civs will distrust you more.
I betrayed the Babylonians when they suspected my units were amassing on his border, and said "Don't worry, just passing through"...move along, nothing to see here! LOL Anyway, a few turns later when he went to war with a city-state I liked I declared war on him. Babylon said I have betrayed my word in telling him I wasn't going after him, and he would make sure the world knew it.
My diplo relations appear to be lessened with other civs (but not city-states). So, that is why you may want to tell the truth to your opponent -- if he catches you in a lie, all other civs will distrust you more.