Apparently, the union felt that beating up or killing the homeless would not do much for its public relations image. In short, the use of violence is the key to the winning of strikes. Since labor historians have almost all been biased in favor of unions, they strongly imply that almost all the violence was committed by the employer's guards, wantonly beating up strikers or union organizers. The facts are quite the opposite. The reason unions are to blame is inherent in the situation.
Violence is disruptive, and is bound to injure the profits of the company.
But the victory of unions depends on making it impossible for the company to continue in production, and therefore they must zero in on their direct competitors, the workers who are replacing them. No one denies that. Everyone surely has the right to quit. But that's not the issue. The issue is whether the employer has the right to hire replacement workers and continue in production.