Gaslighting, the manipulation technique of stating that observable facts are other than what is easily observable as a way of trying to get people to question their own sanity (or at least their ability to observe properly), is an old tactic used in Leftist activism.
The most high-profile / publicly known version is the “War on Christmas” in where concerted campaigns to minimize, trivialize, condemn, ban, water-down, and wipe out depictions, celebrations, public displays, and the federal holiday status of the uniquely American version of the Christmas season are pretended to either not exist or be greatly exaggerated by those who support those acts of war.
The purpose of the tactic is to shame the Paul Revere’s of the issue into shutting up in sounding their alarms so that the thing they are warning about can execute efficiently and successfully.