The only way to tell people what they don't want to hear, is to tell it in way that offers no choice. I will speak of one such way. First, bear in mind that most humans are herd animals. Above all things, they crave a stable sense of belonging, in the company of others who likewise crave such belonging and have agreed upon a general plan to make it happen.
So, if you are the bearer of news which challenges the herd and its stable plan, you must know that the herd's considerable resources will be mobilized against you in order to nullify your message. It is not, in the end, a question of "truth", but rather a collective will-to-believe backed by the power of unfailing repetition and communal reinforcement within an echo chamber.
Your message will take root and grow only if you make the herd disintegrate. Do that, and their power to dismiss your message will disintegrate in tandem. And when people get to this point, they will instinctively cast about in search of a new herd they can join. You know how joiners are. So it is a good idea to prepare something they can cling to, that they will be more readily persuaded to make the jump.