First, he asked you to go to the library together the next morning. As a result, he didn't get up, indicating that he didn't pay attention to this matter and didn't respect you.

Second, if you give him your seat and wait for him, he will not sit when he sees it, which will even disrespect you and hurt you again.

Third, he stood you up, but he didn't take the initiative to explain and clarify things afterwards, which shows that he respects you more.

In a word, he is a person who doesn't know how to respect people and doesn't care about you at all.