I have a statue of a very controversial and considerably blasphemous deity and even though it's replaceable, I'd be upset to see it broken, because it means quite a lot to me. Being a Satanist, I don't really like Christian values, but I'm not going to smash every Jesus and Mary statue I see. As long as they're respecting me, why would I disrespect them?
I think your son needs to be shown some different religious perspectives. Buddha isn't really a considered a god or prophet by some. My mom, who likes to study Hindu-Buddhist philosophies, used the example of the Buddha walking down the street. If some would kill him because of impersonation, I don't think that's really a stance of worship, but a way to respect teachings of a person long past away. An imposter would tint the teachings by pretending he was the real deal.
Your son, although I'm sure he wants to be a good person, needs to understand what that means before he aligns himself with any religion. I don't think destroying other's things, no matter what you align with, is a good thing to do, even if you mean good. He's probably using his beliefs as justification to bring out anger or harmful thoughts to the attention of something else, without understanding what others think about it. I do agree with the others who replied, he needs to see a counselor or professional about this. The teachings he is reading isn't saying he should do things because it will make him a better person, rather it is setting examples in the forms of stories as to why as a Christian, he needs to believe in certain things. Even though I don't agree with the scriptures Christians hold high in respect, I think anyone who reads them should consider the context and background for these stories, as to why the idols were smashed and so on. Stories like those aren't saying that it's good to behave that way, rather the stories are praising the spread of the religion and showing why the minority at the time were angry, and explaining why idols are false gods. Unfortunately there will always be literalists who don't stop to think why they have all the Jesus crosses and if that in itself is an idol of sorts. Christianity is complicated.
But definitely charge your son with financial damages he caused and take him to see someone who can explain to him why his behavior is counterproductive. Hopefully he'll be respectful after he takes accountability for his actions. Maybe some of the Christians here, if you can talk to them, can give him advice of the family stuff as well.