Yes. In the same way that one politely ends a phone call, just say that you want to regroup and will be back when you are ready. Then walk away and find someone else. At a fortress hub such as IAH this ought to be relatively easy. Admittedly a bit harder at a small station. In the latter situation, just politely say that it hasn't been your experience and ask the agent to call or find a supervisor.
The key is to disengage without a confrontation.