I believe you have the far left operators pegged pretty well.
The main ways that this is done is by either declaring the opposing speaker as unworthy of debating ("He's ignorant", "He's stupid", "Fox LIES!") or by declaring his position as anathema ("Racist!", "Sexist!", "Homophobic!", "Hate Speech!") and thus not a fit subject to speak about. Just shutting down the opponent is also a favorite, whether accomplished by shouting over him, or prohibiting him from speaking because of threats of violence.