In this context, Jesus was being told the opposite. He was told He wasn't old enough. Jesus was speaking about Abraham as if He had seen him, yet Abraham lived two thousand years earlier. Christ's critics scoffed, "You aren't even 50 yet! How could you have seen Abraham?" At their scoffing, Jesus dropped a verbal bomb on them and said, "before Abraham was, I am." What was He revealing? He was revealing the fact that He is self-existent and eternal. And instead of bowing to worship Him, this group of men tried to stone Him.
How accepting are we of what Christ has said? When He confronts our idols, heroes, and false beliefs, do we thank Him, ignore Him, or try to stone Him?