The liberals took over the mainline Protestant denominations decades ago. All of them, with the possible exception of the United Methodists, are in terminal decline and are little more than sinecures for liberals with backwards collars, managing real estate assets of dying or dead churches and trust funds that are slowly depleting. So the religious Left recycling their strategy that succeeded a century ago in dominating the now dying denominations on still healthy and evangelical groups like the Southern Baptist Convention and the Presbyterian Church in America. The “wedge” a hundred years ago was modernism and evolution; today it is sexual perversion and “social justice”. The strategy is the same: get your nose into the tent and slowly gain acceptance and later control.
J. Gresham Machen wrote an excellent book on the dangers of the church loosening up to go along with what is considered modern. It’s called Christianity and Liberalism.