I feel my friend is manipulating me. anyone with a knowledge of psychology got any advice for me?

Yes based off of all this information he is in fact trying to manipulate you by guilt. It doesnt take a psychology major to know how to manipulate someone, all you really have to do is take any emotion (fear, sadness, anger, guilt, happyness, etc.) and use it to control someone. For example lets say i have a girlfriend and she wants to go out with a bunch of guys, and i dont want her to but i decide not to say anything straight forward, or decide to atleast ruin the night for her. If i wanted to manipulate her into not going or feeling bad by guilt I could say something like, "well have fun while im sitting alone here with nothing to do." Even if she really wanted to go there is no way she could have a good time if she cared for me because she would keep thinking about the comment i made and dwell on it, therefore I would be controlling her emotions, and actions which would be manipulating her. By threatening to not talk to you he is using a double whammy of Guilt and Fear. He is hoping that by letting you know that he doesnt want you to be with his friend, that you will feel guilty enough to not hang out with him. He is using fear in hopes that you would be afraid of him not talking to you anymore, so that you would stop talking to him. This guy is trying to be manipulating by controlling your emotions, and therefore controlling your actions but remember you can only be manipulated if you let them. My advice is next time he says something like this, do exactly what he doesnt want you to my reasoning for this is, first you dont want a manipulating guy in your life trust me all your life he will be controlling you and forming you to what he wants. My second reason is knowing manipulating people they are all bark and no bite, so he would never carry out his threats in the first place. Whew long answer for a long questions lol