In essentials (including morals), unity; or Unity in morals is not a non-essential, not a non-necessarium
"There is a Reformation slogan that sums up the impossibility here: 'What the law demands, the gospel bestows.' The law demands righteousness, the gospel bestows righteousness, and it does so by bringing Christ to us and us to Christ. He is the living fulfillment of the law, the one in whom all that the law requires is fully and unquestionably realized. His righteousness covers our sin, when we become one with him by faith, but at the same time, he lives in us, which means that righteousness dwells in us, alive and triumphant, and we begin to live a new kind of life. But if the gospel bestows what the law demands, then without agreeing substantially on what the law demands, we cannot agree on what the gospel bestows. And pushed to the end, such disagreement will easily turn into disagreement about Jesus Christ and his saving righteousness."