The Gospel is the Good News. But this news isn’t really that good until you know the bad news.
The bad news offends people. The bad news is that all people are wicked. We’re all naturally evil, no ifs, ands, or buts.
Why do you need to know the bad news before the Good News? Because what good is this Good News unless you know something is wrong? What good is medicine if you aren’t sick? What good is being saved from wickedness if you don’t know it’s there?