Grace8....There are a couple of reasons....
1. deflection....putting you down is a way of taking the attention and spotlight off of him and his actions...and putting it on you....
2. leveling....when a person feels bad about themselves in some way....a way to deal with it is to bring the other person down....by pointing out some flaw (real or fabricated) of theirs....
Some will try to bring themselves up by acting superior or being bragadocious....
I hope that you will keep reading, and learning.....the thousands of real life stories, here on the forum...the stickies at the top of the main page...and the recommended books and articles....
there is so much to learn.
Knowledge is power.