Pray on it.
If this is the first incident, I would be willing to put forth the effort to try to make it work out. He should know that he is on probation. But, if he does not want to be there, then he should not be made to come... that is unhealthy for everyone.
If you give him another chance and he fails to comply... then he should not come back. Learning experience for everyone.
If you give him another chance and he makes it... then you have helped him for the rest of his life.
Question: Does your unit give a "new scout briefing" to scouts and parents? Like, "we will not tolerate this, this, and this"...