Passive ethics teaches us what not to do through prohibitions while active ethics tells us what we should do. Ethics is a trust factor in society and without it the social relationships embedded in society begin to break down. Understanding the difference between the two helps us to understand when ethical behavior is above standards or part of standards.
When we are prohibited and we adhere to that prohibition we are passive. We must only NOT act on something to be ethical. We simply don't engage and show a level of self-control.
We may see this example with a group of people harassing another person. If you do not engage in such behavior you have fulfilled your ethical requirements in that situation.
While not acting is helpful it doesn't stop, thwart or change the behavior of others and is therefore passive and of a weaker form than the more aggressive active ethics.
Active ethics can create risk and harm to those seek to thwart wrongdoing and therefore requires a level of sacrifice. One must act beyond their personal well being for a greater good.
We may find this in an example of corruption or institutional wrongdoing where doing nothing and turning a blind eye means one did not participate but was aware such acts occurred. Once someone is aware than to fight against such corruption or stop it with one's own hand is a more risky proposition.
That risk puts the ethical act at a higher form than that which is seen by simply not engaging.
This problem can be compounded if both the institutions and the people who believe in those institutions have come to accept immoral and unethical behavior as part of their daily life and try and defend that life.
It is the first of such people who speak out that usually are inflicted with societal anger and punishment. Changing minds is a dangerous and difficult proposition.
When faced with an ethical dilemma a person must decide to engage in the immoral act, abstain or fight against it. The moral character and personal strength will determine which route someone will take.