Earlier quoted context omitted.
No. A strike is a weapon of last resort -- you have to have the ability to use it, but you don't want to use it. Much better is when both sides are negotiating rationally. When a union perceives that the company is not negotiating rationally, that's when they take a vote to authorize a strike. Then, hopefully, the strike doesn't happen... but it's available.
Is firing the entire union protected under labour laws in at will employment states?
Seems that if the employer can hire replacements quickly enough, the strikers don't get their jobs back.
"Economic strikers defined. If the object of a strike is to obtain from the employer some economic concession such as higher wages, shorter hours, or better working conditions, the striking employees are called economic strikers. They retain their status as employees and cannot be discharged, but they can be replaced by their employer. If the employer has hired bona fide permanent replacements who are filling the jobs of the economic strikers when the strikers apply unconditionally to go back to work, the strikers are not entitled to reinstatement at that time. However, if the strikers do not obtain regular and substantially equivalent employment, they are entitled to be recalled to jobs for which they are qualified when openings in such jobs occur if they, or their bargaining representative, have made an unconditional request for their reinstatement."