Liberal groups have always treated non-incumbent conservative positions as illegitimate. Thus they do not substantively engage with them, debate or engage with their practitioners, provide platforms or space in their publications, etc. 

Conservatives, by contrast, frequently give respectful hearings to liberal views, engage in substantive debates, etc. They fail to appreciate that even engaging with heterodox views in order to refute them bestows a kind of legitimacy on them. If those ideas ever achieve supremacy, however, conservatives will soon find that their own long held views will be deemed illegitimate. All debate and engagement will be ended.

We should be very thoughtful about how we engage with opponents and situations in order to avoid accidentally legitimizing the illegitimate.

John Piper, "Prayers Cause Things": https://www.youtube.com/watch?v=krzwmhDMvv8

Rod Dreher on Dialogue: https://www.theamericanconservative.com/dreher/the-orthodox-left-wails-schmemann-lecture-orthodoxy-rod-dreher/

On Sam Nunberg's drunk TV interviews: https://www.buzzfeednews.com/article/zoetillman/former-trump-adviser-says-screw-mueller-subpoena-in-intense