The lesson I got is that Barabbas is exactly the kind of man that the world as a whole prefers over Christ. They want the badass, the rebel, the guy who fights with his fists against his enemies - the typical ideal of a hero. They don't want an innocent man or one who turns the other cheek. They mock him and spit on him and tell him to "man up". And it's not just Jews who sinned here. It's all of us, every time we cheer on a hero like this or promote "freedom fighters" like this (yes, even my own country like the USA, which is founded on these very things).
And even more to the point: The ideal "badass" hero is ultimately Satan himself. He also rebelled. The only people I see who are honest about their liking for him are satanists.. who call him a champion of freedom and individuality.