No it isn't actually. Kidnapping doesn't have an exact definition in most jurisdictions simply because it has variables, and being held for "nefarious purposes" is not a requirement. Even in the "Model Penal Codes" (which aren't actual codes but an example designed by the American Law Institute) they include "interfering with a governmental or political function" in the list of purposes. In this example, was the woman seized? Yes. Was she physically moved? Yes. Was she held against her will in order to silence her? Yes. Did she have the right to speak in that forum? Yes. Was she recognized by the person running the town meeting? Yes. Did the police have any legitimate reason to seize, remove, and silence this person? No.
That's called kidnapping among other crimes.