The question for cable news show hosts:
More often than not, do you really listen when people are speaking to you
instead of just waiting for your turn to speak?
No, I’m sorry. While that is a legitimate question, it is not THE question. This is the question:
Will you please stop butting in and cutting off your guests when
they are trying to answer the question you just asked?
Now the first question is the question.
bobdahl 
More often, I hear politicians evading the question and seguing to something on their own agenda, or to a different issue altogether. In those cases it is appropriate for the interviewer to interrupt for the purpose of bringing the conversation back on topic.