I would explain the content to them. Explain all the different sides and my personal views on it as well as direct him to content with opposing views. Then I would let him form his own opinion.

My job as a parent is to help him understand. Not to build a bubble.

As for violent content I would tell my kid to just watch out for that and that the content is unpleasant. It's his choice whether he wants to see it. Usually at that age adult content or violent content is uninteresting or unpleasant so kids tend to avoid it anyway.