"ReconcilingWorks: Lutherans for Full Participation" is an organization that "advocates for the full inclusion of lesbian, gay, bisexual, and transgender Lutherans in all aspects of the life of their Church and congregations." (see here) And his church has now become a congregation that "welcome and affirm people of...every sexual orientation and gender identity" (see here)
Americans view on gay marriage changed, for the most part, because of the decline in Biblical belief and the normalization of homosexuality brought into our homes through the entertainment we watch.
If you are not reading your Bible and you study or sit under the leadership of liberal teachers, pastors and bishops who support homosexuality (and other liberal theological positions) you are in danger of compromising your Biblical beliefs and conforming to their position.