Replying to Is my brother to blame?

So we're in the park at a medium sized jump where you can't see the run out, some kid hots the jump and crashes, just slides out of a 3. The kids dad puts up and X with his POLES standing 2 meters beside the jump. Some guy at the top tells my brother to go, and my my brother being Dyslexic and needing glasses doesn't see the x untill it's too late. He landed and avoides the kid, but got yelled at about how he's retarded by the guys dad. Is it his fault?