In defense of this joke, I will say that it was intended to make fun of the winner-take all mentality within a society that is hyper-competitive via a reducto ad absurdum, but, by the potential misuse of it to demoralize people who are in opposition to Fascism, I can also understand as to how and why it is that a person could take offense. The purpose of this thread is not to either defend or admonish this joke, but, rather to put to question as to whether or not humor can be too cynical or bleak.

The purpose of this thread is not to either defend or admonish this joke, but, rather to put to question as to whether or not humor can be too cynical or bleak. — thewonder

Much would depend upon your definition of humor.
If you count humor as the ability to appreciate and express humorous things then jokes that are cynical would not usually be counted as funny, UNLESS it is also accepted that the mocking of others is acceptable. And we are not allowed to do that nowadays.
Most adult jokes tend to make fun of others, a person or group, that are not part of the tellers in-group. And they do often to lean towards degrading them, either making them look stupid or abnormal in some way. But the funny thing is that most peoples have their own jokes that do exactly the same to the ones that tell jokes about them.

Can anything be too cynical to be a joke? No, if something makes people laugh then it is not too cynical. But cross the tracks and see if they laugh on the other side.

Should jokes be cynical? Not if they really do cause harm to people. Telling jokes about Jews is one thing, I learned a lot from an old Jewish friend. But telling jokes about the concentration camps is going a bit to far if it is meant to make the suffering of the people look funny.
The old guy I knew actually told me a joke about one of those camps, but it was the Jews that made fools of the nazis in it.

Well, the intention was to get at more of an existential absurdity and not to mock anyone. I think that they can be too cynical by that account.

So,

"Sometimes your best just isn't good enough.", juxtaposed over an image of the Warsaw Ghetto Uprising. — thewonder

would not appear to mock anyone.

Maybe it is a jab at the bosses that came up with the signs you mentioned, but they are a group. Thus you were, possibly unintentionally, mocking their way of thinking.
A wild guess by any of them, might be that you consider them to be nazis.

Not, not the case.

As stated, I have no intention of posting this Demotivator and only came to wonder this after thinking about it. It's intended to make light of what it reveals about the human condition, that failure is not an option when survival at stake, and not to make fun of Jews or people who died during the Holocaust. That you interpret it as your standard white nationalist schadenfreude and not in the Cards Against Humanity vein that it is intended is just indicative to me of that I'm correct in my assumption that it's just too bleak. If you substitute the Warsaw Ghetto Uprising for any failed revolt, you will run into the same problem. Even a fictional one wouldn't go over well.

The joke isn't terribly offensive in its own right. Perhaps, I could've chosen a different context, but, I've already elaborated upon what is also untenable of that. It's that what it reveals about the world is just too dark for anyone to consider to be funny. It's supposed to make light of the Absurd. It's supposed to be as if I have just told you something terrible and in my sardonic way of having done so you're supposed to laugh as a way of letting go a certain angst. Because it does have this deep, dark element particular to black humor, any old person will just take the kind of surface offense that I fear could be utilized in facilitating white nationalism.

As it concerns my employer, I actually think that I now have one of the better jobs that I've maintained. I just think that those phrases are entirely absurd. The joke is a rather extreme form of reducto ad absurdum. It could just be that it's not a very good joke, but I honestly suspect that I've just crossed a certain threshold of darkness. I think that it's kind of funny, but, for just about everyone, it's just too dark.

As stated, I have no intention of posting this Demotivator and only came to wonder this after thinking about it. — thewonder

Maybe that was a good decision. I know that your intentions were not evil and my point was not supposed to be aggressive. It was just to point out that humor is usually a part of every group's value system, what actually counts as humor can be very different between different groups though.

It's supposed to make light of the Absurd. — thewonder

The truth of your statement cannot be faulted, is not absurd. The fact that sometimes, no matter how hard you try, you are going to fail is an objective statement about the conditions in the world. To make jokes about the truth can be hurtful.

Dark humor, mixing the distasteful with the funny, can be very entertaining. But it can also be disgusting to some. But most would be bothered by jokes about violence against others, unless of course the joke is about lawyers or politicians.

As to whether someone would take your work and use it as a tool to promote "white power", I really cannot see how that would happen.

There are two kinds of people, to my estimation, who tend to appreciate black humor, the first being people with a general interest in something like Existentialism who would often be described as being fairly "nihilistic" and the second being people who are likely to do things like listen to Black Metal. Though not all Black Metal fans are as such, I could see an occult Neo-Fascist using the joke as kind of an implicit threat and it being disseminated within white nationalist circles. In rather arcane sets of society, Nihilism is occasionally used as a means to demoralize people who are in opposition to things like Fascism, and, so, Nihilist humor is somewhat exploitable by that account. I'm not really a Nihilist, anyways, though.