The most accurate response to the question about the impact of the Haymarket Riot on union membership is:
After the riot, people saw unions in a negative light due to the violence that happened.
The Haymarket Riot, which occurred in 1886, was a significant event that involved a labor protest advocating for an eight-hour workday that escalated into violence. As a result, public perception of labor unions was negatively affected, leading to a decline in union membership. People associated unions with radicalism and violence, which caused many to distance themselves from these organizations.