His sin was declaring to the church that they are to seek to save lost souls through the sharing of the Gospel and if $$ are needed to support outreach then the Church should divest its holdings to support outreach ministries.
He also made the statement that our Lord Jesus had no place to lay His head and no earthly possessions, therefore how could the Church justify its oppulence while the lost are dying and going to hell if $$ was the reason for lack of evangelizing the lost.
His bigger sin was in seeking to purge the Church of gay priests.