Dealing with a Friend's Communication Issues and Temper

So, a friend of mine has issues with communication and takes a little while to get his thoughts all out. He got a bit upset and lashed out at my group. I got up and moved out of anxiety and a bit shaken up. He got upset because he thought that he offended me. That wasn't necessarily the case. I have been trying to think about some other things to do to help him out. He can get stingy sometimes and him being stingy makes it harder for me to want to work with him. He has many likable qualities but however he does have a temper.