I think this my newly investor friend was out of pride and just wanted to make this other guy feel regret but does not know the dangerous implications he has just made upon himself and his Bitcoin assets.
It is unfortunate for investors who lives this life of proving themselves to people just to make them believe on their investment.
We don't know if he did what he did out of pride or by sheer attitude of trying to convince the doubting friend about bitcoin with a proven evidence directly from his wallet. One thing is here is certain,
you didn't preach to him about privacy with bitcoin and how important not to comprise on it.While we brush people up about how profitable bitcoin can be to them if they invest long we should with that approach enlighten them too on the tenets of how to safeguard their investment from public notice because privacy is peace. The more people don't know about your finances the more peaceful and secure live becomes for you.
I wouldn't blame the OP in this case because he didn't mention privacy to his friend. Even if it is not bitcoin but another asset/investment, it is his decision whether to share it with others or not because if he had a boastful personality, he would do it with other assets as well, not just with bitcoin.
But you're right, we don't know what his real intentions are, is he bragging or just wants to convince the other friend. But regardless of his intentions, revealing his assets to others is a huge risk even if it is not bitcoin. Not only should we keep our bitcoin investments a secret, but we should also refrain from flaunting our wealth under any circumstances and to everyone.