Employers and clients are also dangerous. If they don't pay, or place excessively onerous conditions on providing payment, it can put people in dire straights.
On the flipside, as an employer, employees and contractors are dangerous, as they may fail to provide the agreed upon services in a timely fashion. Balancing the interests of both sides in these matters is why industrial relations law is so fraught. Our brains are wired for good/bad thinking, so most people fall into either "employees noble hard workers, employers evil robber barons" or "employers noble job providers, employees evil union thugs" false dichotomies. In reality, neither side is likely to be malicious: short sightedness, selfishness and sheer incompetence are all more likely explanations for seemingly hostile acts than deliberate malice. And sometimes it's none of those things, but merely a difference in priorities (e.g. sacrificing some jobs for the sake of preserving others - when a company goes under it generally sucks for everybody involved, except maybe the actual robber barons that have already made sure they got their cut by lumbering the company with excessive debt)