In a way, I think coercion is a requirement to be ethical. Ethics is determined based on what current society believes to be the right thing to do. We see that there are a variety of different cultures and ethics around the world, which would indicate that humans wouldn't just automatically follow a universal set of rules.
Thus to be ethical in your society, usually means you must follow the rules determined by a collective group of your nations ancestors or you will be shunned/jailed/harmed/etc. Which is essentially coercion. "Act this way or be punished."
But there is a difference in behaving ethically and behaving legally. While there may be consequences for behaving unethically (IE "I won't do business with them because I do not feel they are ethical"), society generally only overtly punishes those who do things that are illegal.
It is the other way around.
White collar crime might be illegal but most societies would definitely punish a murderer either legally or illegaly. Social stigma is a MUCH more serious thing than legality of action.