Plausible deniability is the sleight of hand used in the world of politics to avoid unpleasant consequences. "I didn't know," "I wasn't involved," "it's not my fault" ... that sort of thing.
At a more personal level, often gussied up by adults, is the childhood version: "The dog ate my homework."
My view is this: The fault I see is my own fault. I am responsible.
Some take this to mean that because they can see the fault, they should therefore be wary of "casting the first stone." We're all at fault, the argument runs, so let's go easy on each other.
But I think that if you see your fault and work your ass off to correct it or to try not to repeat it, then there is no reason for not calling out the same fault seen in others. A mistake is a mistake ... make it and try to correct it ... that is our practice. When someone gets stuck repeating over and over again that "the dog ate my homework," I see no fault in calling bullshit what it is.
Work to correct. And then work to correct what you have failed to correct. But don't imagine that bullshit is any the less bullshit because we all step in it.