Visitors who arrived at the Whitney Museum of American Art on Friday night to view the works in this year’s politically tinged Biennial had to pass by a raucous demonstration that was not part of the official programming.

About 200 people squeezed into the Whitney’s lobby, in the ninth of a series of weekly gatherings to protest a museum board member whose company sells tear gas that activists and the art publication Hyperallergic said had been used on migrants at the Mexican border.

It was the most recent episode in a prolonged public debate — involving letters and pronouncements by museum employees and officials, scholars, artists and art critics — over the board member, Warren B. Kanders, and his company, Safariland.

According to Hyperallergic, photos showed tear gas canisters marked with the company’s name at a site where the American authorities used tear gas last fall to disperse hundreds of migrants running toward a crossing that leads from Tijuana to San Diego.