12 is too young to be a "conservative" or a "liberal" for that matter. He was simply parroting an adult in his life.
Regarding the OP, I doubt if it we have heard the full story.
Regardless of whether he is an adult or a child, he has the constitutional right to free speech. It is unfortunate he had that happen via a site that isn't obligated to enforce constitutional rights. Regardless, he has a right to take on the political views of his parents if he so desires.
Those people who agree with Facebook did, will attempt to justify their position by saying "we haven't heard the full story." I think you could start by actually reading the article.