I must have missed the posts in which people were advocating "casting" homosexual children out of their lives. Although I did read comments of social liberals accusing some of that using straw man arguments.
I believe that might have been Jesus Christ, and not an FR poster.
"He that loveth father or mother more than me, is not worthy of me: and he that loveth son or daughter more than me, is not worthy of me."
Now while that's not an explicit command to action in and of itself, the action of casting out the sinner is easily more Scripturally defensible than ignoring the sin.
Those presuming on the love of Christ should read the seven letters to the seven churches that open the book of The Revelation with the understanding that these are epistiles dictated to St. John DIRECTLY from the mouth of Jesus Christ.
Investigating the historical fate of those Churches should prove very illuminating.