My guess is that they think this reflects poorly on the interviewees - at least, in the eyes of their viewership - and it also serves to indoctrinate their viewers against similar conversations with their own acquaintances. If somebody you trust tells you that something you said is absolutely bonkers and wrong, you might question yourself, but if they say that to you after you already heard similar objections and arguments being ridiculed on your favorite TV channel, it seems less likely to make an impact.