This is a person that is incensed you had the nerve to turn down their proposal of friendship.

He knows that in having you as a friend, you are an easy ego boost for him whenever he needs it.

In the future, when he has a fight with a girl he is dating, he turns to you, his platonic friend, to make him feel better about the fight by giving him emotional support.

Whenever there is a dry spell in dating, he turns to you to boost his ego by telling him about how handsome he is, and how any girl would be lucky to have him as a boyfriend.

He knows that you like him romantically.

As a consequence, he knows that regardless of the fact that you are technically his platonic friend, there is a part of you that continues to like him romantically.

Deep down, you are thinking that somewhere along the line, he changes his mind about you, and pursues a romantic relationship with you.

He knows to keep dangling this carrot in front of you every now and then by occasionally giving you a compliment or flirting with you.

This is how he gets to keep you on his back burner.

When you didn’t accept his offer for friendship, he got upset that you had the gall to refuse it.

You actually took a stand by turning him down.

This was a show of power he didn’t think you were capable of.

Given that he knows you like him romantically, he was expecting you to jump at the opportunity to become his friend.

From there, you bide your time, waiting for him to change his mind about you and consider you as someone with romantic potential.

He has been in this position before with a girl, but the roles were reversed.

There was a girl in his past that he liked romantically who he ended up becoming friends with, aspiring to become someone she dates in the future.

He remembers how he hung on for years, waiting for her to change her mind about him.

She never did.

Romance never happened between them.

Nonetheless, he wants you to do the same as he did.

He wants you to become his friend and stick around for years, waiting for him to change his mind about you.

All the while, he has no intention of getting romantic with you and uses you for the attention and ego boost.

When you didn’t accept his offer for friendship, you took the power away from him.

You had the boldness and the gall to turn him down.

As far as he is concerned, you should have been kissing his feet in gratitude for his offer to make you his friend.

Yet, you didn’t.

Up until that moment, he had been basking in all of the adulation.

He felt so empowered by how much you liked him.

This made him believe that he was in full control.

When you didn’t accept his offer for friendship, he was hit with a massive dose of reality that deflated his ego.

That upset him.