Take actions to correct situations where you feel like the other person might have taken offense or perceived you as rude. The sooner the better. If you're in a professional environment, send a quick IM or email. It can be as simple as: "I hope I didn't come off as rude earlier. I stutter pretty severely. Sometimes people are offended when I am abrupt. Please accept my apologies if you felt I wasn't being courteous." If your friends are telling you that you need to work on this, put some work in on this.