Morality taught by some
Is there a simple answer for why many "mainline" Christian denominations, including the largest Lutheran body in this country, either remain silent or now actually officially teach morality contrary to Scripture, e.g., abortion can be tolerated, homosexual marriage? Assuming congregation members are aware of and understand what's being taught, are they truly Christians? What about the leadership?
Much can be attributed to a denial of the authority of Scripture. The clergy of the churches reflected in your question are trained in the historical-critical method of biblical interpretation. That method rejects the verbal inspiration of the Bible and opens the door for people to say that the Bible contains mistakes, inaccuracies and contradictions. That method rejects the idea that Matthew, Mark, Luke and John wrote the gospels that bear their names. That method leads people to look at Bible passages that are not popular today and say, “It would not be loving to take these words literally, so let’s see how the Spirit of God might lead us to understand and apply these words differently in our day and age.” You can see that it is people’s wrong attitudes toward Scripture that lead to false doctrine and the approval of sinful actions.
You and I can judge actions—and we are to do that by lining up people’s actions against God’s word—but we cannot and dare not try to judge hearts. God alone knows whether or not there is saving faith in people’s hearts.
What you and I can do is testify to others about God’s Word: that all of it is true (John 17:17), that all of Scripture is inspired (2 Timothy 3:16) and that the words the human biblical authors wrote were the words they received from God (1 Corinthians 2:13).