There was nothing to be defensive about — Ted just warned him against acting like an out-and-out bachelor in front of Robin, and Barney overreacted and was an absolute dick about it (and needlessly so).

Moral of the story: get knocked up in your teen years.

Moral of the story: get knocked up in your teen years.

How dare you!

How dare you!

Not just emotional vulnerability, though that does tend to make a man more appealing if you're looking to lock him down. Other things that made his persona attractive are that he was a billionaire and was married but still not completely over his wife so not entirely available — you have no idea how appealing that can…

Not just emotional vulnerability, though that does tend to make a man more appealing if you're looking to lock him down. Other things that made his persona attractive are that he was a billionaire and was married but still not completely over his wife so not entirely available — you have no idea how appealing that can…

To answer your initial question, it's usually for the reasons outlined in this episode: to not lose face in front of other men, and to turn women on.