I understand how you feel..bcoz he is also my beloved PROPHET...any insult on him..it pains me...but what to do..there are people who doesnt understand his importance to us...MUSLIMS...eventhough how much you explain to them..there hearts are closed...blind to any logic..
So..stay CALM...dont go down to their level...the more you react the more they will tease you and make you mad...May ALLAH bless you....!