I don't think they should! In fact, if you have a problem with it, I would recommend you work on (re)organizing private sector workers for greater job security, better wages, and benefits. It'd be rather more productive than beating up on unionized workers and crying like a child whose ice cream cone went plop and now wants someone elses.
How has that worked out for, oh, say, the United Auto Workers-- or, hmmm, I don't know; the textile industry? Better wipe my ice cream off of your shoe, junior--and shine mine while you're down there.