[infamouscow]

Derision is legitimate way to change behavior when other avenues fail.

A reasonable person that's acting maliciously can be reasoned to stop their behavior.

An unreasonable person that's acting in good faith cannot be reasoned to stop their behavior because they are stupid.

If after attempts to reason with the unreasonable fail, it is not an insult or ad hominem attack to explain the person is acting stupidly.