I find that I work really hard at trying not to step on that escalator towards a conflict. Some things that have worked really well for me have been to ask the student to go take a walk or to get a drink, which gives time to cool down. Upon return, I ask the student to schedule a time to discuss the issue. If it's urgent, I ask if it's private and if we should go into the hall, or if it can be handled at my desk. I also make sure I repeat the student's concerns back to the student as we are discussing things. For example, 'if I am understanding you correctly...' works well. ACTIVE LISTENING WITHOUT A DEFENSIVE REACTION IS KEY. Remain calm; you are the adult. If you allow the bulk of the class to see an escalation of your temper, you will loose their trust despite how they feel about what their peer is doing or saying to get that rise out of you. Do not hesitate to apologize when it's called for. Damage control goes a long way, as does being approachable rather than defensive.