It's frowned upon to say unkind things about people.
Kent does not like his country's leader at all, so he complains about him.
Kent wants to discuss with his friends.
Kent decides that he should save his rants on the leader for when it's appropriate to do so.
Kent rants about the leader and how stupid and such he must be.
Kent's friends appreciate that he's not ranting about the politician right now.
Kent's rant bores is friends who don't care about politics and don't like the rudeness.