Pierre's conversation with vicomte

"He could not do that. The people only gave him power that he might rid them of the Bourbons and because they saw that he was a great man. The Revolution was a grand thing!" continued Monsieur Pierre, betraying by this desperate and provocative proposition his extreme youth and his wish to express all that was in his mind.

The above quote. This is the conversation that Pierre has with the vicomte at Anna Pavlovna's soiree where he says that Napoleon was a great man. Can someone help me out by explaining how Pierre is betraying his extreme youth and his wish to express all that was in his mind? What does this mean? I would greatly appreciate anyone who could explain this for me. Thank you and have a nice day.

Not entirely sure, but I think Pierre is simply showing how naive he is by trying to blurt out every single opinion he possesses. He has not been exposed to high society soirees so much before, and does not know how to behave. Indeed, he embarrasses Anna Pavlovna significantly throughout the soiree because, as the perfect Petersburg society hostess, she feels obliged to keep him out of trouble, and makes several attempts to steer him towards more sophisticated conversation.