If they welcomed their drug addicted son and his dealer into the family in front of young children no one would be celebrating their reaction. This is only an issue because celebrating sexual destruction is what the world wants.
“He is our son” is absolutely not the justification for the scenario I painted. The justification, which is indeed a mandate is the Church’s teaching that the homosexual must be treated with dignity. If one movement was made betraying their sinful relationship, the family would have to ask them to leave. As long as there is a “don’t flaunt, don’t mention” rule which is obeyed, their presence alone could be acceptable. Tough situation.