Jesus rebukes the Pharisees for their hypocrisy. Their priorities are on minor and outward things and parading their own piety. Their like killed the prophets, and will again in a final conflagration that brings all righteous blood down on them as they kill the only Righteous One.
How this is about Jesus
This is the final rebuke Jesus gives on His own terms in the temple in the last week before His death. He is prophet, here, declaring the sin of Israel, past, present and future.
Sins this reveals
Worry what others think of our piety.
Getting caught up in minor issues instead of keeping the main things the main things.
Scapegoating people who are speaking the truth, but who do it in a way that hurts or embarrasses.