According to psychologydictionary.org, cognitive dissonance is "a state of conflict occurring when beliefs or assumptions are contradicted by new information ... the conflict produces feelings of discomfort, which the individual seeks to relieve by reconciling the differences, by convincing himself they do not exist, or by adopting some other type of defensive maneuver."
The SLO Women's March organizers had women (via the San Luis Obispo Police Department) removed wearing "Believe Mothers" shirts and holding signs advocating informed consent, parental rights, and vaccine safety from their "open to the public" rally.
Why were these women unwelcome at an event whose mission is: "to protect women's rights, human rights, our safety, our health, and our planet"? Are mothers' rights not women's rights? What of children who've experienced adverse vaccine reactions? Are their rights—to education, to health—not protest-worthy? Why were signs objecting to glyphosate in vaccines unwelcome? Protesting pesticides in our food or parks is acceptable, but not in vaccines?
Clearly their messages made the organizers uncomfortable. Information that challenges one's belief is disconcerting, and they reacted with defensive maneuvering. They sought relief in convincing themselves that those women didn't exist. A revealing reversal of roles.
Perhaps it is time for the organizers to re-evaluate their guidelines: "Your signs are your personal expression of values you are fighting for ... signs address your truth, and why."