(mc)which of the following events damaged public support for the labor union movement during the late 19th century? the opening of ellis island the pullman strike the triangle shirtwaist fire the haymarket square riot

The Haymarket Square Riot.
This was because as the protesters were peacefully manifesting, an unknown person through a bomb at the police, killing seven policemen, four protestors and injuring scores of people. The general public then became skeptic of the labor union movement and became more supportive of the police.