If people just ignored Fox news lies (as just one example), Fox news lies would get far less publicity and attention and propagation. A defamatory statement is bait. Reacting to it in any way desired by the person making it is taking the bait. Then they can escalate, because they know one is on the hook. To respond forcefully, especially with righteous anger, most often gives them exactly what they want (the opposite of what you are claiming). This is well documented, basic psychology. For analysis of extreme versions, in chains of interactions leading to serious violence, read "The Gift of Fear" by Gavin De Becker. Often enough, any response is taking the bait. There can be nuance in some cases - a simple, calm statement that the claim is incorrect may confound the attacker, who needs a more emotionally driven response to escalate from. But an unnecessarily forceful response is just more evidence, to those who want to believe the false defamatory statement, that it is true. In any of these cases, it is one person's word against another, in the public arena, and people will believe the one they want to believe. We have seen clearly how a person can lie and lie and lie (among other egregious acts) and half the voters still vote for them for POTUS. Manipulators make outrageous statements to start a cycle of response and escalation with their targets. That's their game. The target cannot "win" by engaging in the manipulator's game. The target has to choose to play by different rules. Whether the manipulator's statement is "true" or not is mostly irrelevant.