What are "good men that do nothing" called?

"The only thing necessary for the triumph of evil is for good men to do nothing." -Edmund Burke

Is there an idiom, phrase or preferably a single word that we can call people that could have helped but didn't? Bystanders don't necessarily have help to give. Cowards aren't particularly helpful either.

Addendum:

For example, once EMS has arrived on scene, bystanders are encouraged not to try to help, unless they're a nurse and therefore have the necessary skills to, and sometimes even then so. If in The Service, I would not want a coward (a liability) next me holding the line. Not to take anything away from these great answers, or to insist on a non-militaristic point of view, I would like to veer into the commercial or civilian realm in which I find this quote most often alluded to, E.G., "If we all gave 5 cents we could cure cancer tomorrow." Pretend most of us did give 5 cents and we did cure cancer, but you didn't give. You are now a(n) ____?... yes, I know what we call them, but what is their proper designation?

Solution 1:

Per Merriam-Webster:

shirker: One who neglects his duty, responsibility, or obligation.

This assumes that involvement is obligatory (even if not assigned). If such was the case, avoidance — as in, not actually helping — is shirking.

The only thing necessary for the triumph of evil is for shirkers to shirk.

The problem to answer is inherent in the question. It is the difference between could but didn't vs should but didn't.

As I mentioned in my comment, bystanders works as a term because anyone who isn't participating is a bystander. Coward has an implication of being afraid of doing the task.

Observing the crowd, there was no difference between the bystanders and the people who could have helped but didn't. But they themselves knew. There were the shirkers: the ones who should have helped but didn't, the cowards: the ones who were afraid to get their hands dirty, the apathetic: the ones who just didn't care, and people who just liked to watch the flames dance.

Solution 2:

Enablers

In the context of "all that is necessary for evil to triumph, is that good men do nothing", these good men doing nothing are enabling evil to triumph.

In a negative sense, "enabling" can describe dysfunctional behavior approaches that are intended to help resolve a specific problem but in fact may perpetuate or exacerbate the problem. A common theme of enabling in this latter sense is that third parties take responsibility or blame, or make accommodations for a person's harmful conduct (often with the best of intentions, or from fear or insecurity which inhibits action).

The practical effect is that the person himself or herself does not have to do so, and is shielded from awareness of the harm it may do, and the need or pressure to change. –Enabling, Wiki

TFD: enabler

4. To behave in a manner that facilitates or supports (another's abusive, addictive, or self-destructive behavior).

Solution 3:

In the context of your quote, I would suggest cowards, or future victims. See also, 1984 by Orwell and First they came... by Martin Niemöller, the text of which varies - but one version is,

First they came for the Socialists, and I did not speak out— Because I was not a Socialist.

Then they came for the Trade Unionists, and I did not speak out— Because I was not a Trade Unionist.

Then they came for the Jews, and I did not speak out— Because I was not a Jew.

Then they came for me—and there was no one left to speak for me.

Another possibility is do nothings from dictionary.reference.com -

a person who chooses to do nothing...