On a local level, I've witnessed politicians and government officials holding reasoned, civil conversations with people who don't see things their way. But in "the big show" things are a bit different. .
Celebrity politicians seem to prefer hyperbole, over-simplification, mockery and reliance on well studied guidelines from the group and its hierarchy. Why do you suppose that is? Why is it that the more under the microscope a politician is, the more likely you'll never hear them engaged in a substantial, open conversation?
It may have evolved as a form of professional courtesy. If you aren't confident in your assessment of an important issue, but you want people to think you are, you'll do whatever you need to do to keep the conversation from getting too in-depth, especially on national television. Now with the advent of video phones and YouTube, you would have to be on gaurd 24/7. You might have serious discussions in private, where nobody can hear you be wrong, but you'd avoid it like the plague in public.
Perhaps the mindless bantering back and forth is a convenient means for both parties to a public conversation to avoid exposing their own ignorance or weakness on a subject. Have you ever seen a nationally prominent politician turn to another one from another party and say "Gee Bob, I never thought of it that way. You're absolutely right. I was mistaken." I've never seen it in my lifetime. In the history of modern telecommunication, doesn't it seem odd that there's not a single recorded instance of a nationally known politician having his or her mind changed. Can all these people who are supposed to be professional influencers be so inept at the art of reason that in 50 years, nobody's ever made a point well enough to change a mind on television or even camera phone?
More likely, it's an "industry standard". It's just become accepted that you don't have productive conversation in public. Some might suggest they're just talking down to the level of the general public. I believe many more people would tune in and pay attention if the conversation were more intelligent. But intelligent conversation is risky. Especially if your method of reasoning really isn't on solid ground. If you look or sound foolish, your career could be in jeopardy. Safer to keep the conversation on an emotional level.