That was a HUGE deal of him burning it, and it showed Robin that Barney was ready for marriage. But he didn't burn it. And all it took was a 30 second conversation for her to be cool with it? Bull shite.
At first, I was kind of annoyed by that. But the more I thought about it, the more I realized that Barney was right. It's actually more consistent for his character to have done that. He was right about Robin falling in love with what he is, not some new improved version of him. Even though it was a big deal to burn the book, ultimately it was still just another part of a play that Robin fell for.
She can be mad at herself for falling for it, but it's not like she didn't know what she was getting into.
I don't feel like that's the end of it though. She's going to reconcile that she'll have to deal with that part of Barney's character and come to accept it. What will be his part of the quid pro quo there? Her barren womb?