If you have annoyed another leader to the point when he won't talk to you (e.g. you have been at war for a long time but have recently signed a cease-fire which you are now trying to revoke) then is it possible to declare war on them? This happened to me recently and every time I tried talking to them I got the "we have had enough of your worthless chatter...", with "farewell" being the only option to click, meaning that I couldn't say "let's discuss something else" -> "WAR". Am I missing something obvious here?