But jack-shit and its profane peers flout the rule. You can say You don’t know jack-shit, using it in a negative context, but you can also just as easily say You know jack-shit. Same with dick—I don’t draw dick unless the price is right is fine, as is I draw dick unless the price is right.
There seems no reason that the term profane should be used here. This is common vulgarity (or, cussing), and, as such, is not codified by any rules or protocols.
I cannot imagine how the author can claim that not know jack-shit means the same as know jack-shit; unless jack-shit (with a hyphen) is a proprietary word the author feels he owns.
The same is so for draw dick or, plain dick. Perhaps the author believes he has an understanding of these words. If that is so, he no doubt knows far more about them than the one who ordinarily issues them.
If any sense is to be made from such vulgarity, one general principle need be observed: cussing=negative.
But negative and its profane peers flout the rule. You can say You don’t know negative, using it in a negative context, but you can also just as easily say You know negative. Same with negative—I don’t draw negative unless the price is right is fine, as is I draw negative unless the price is right.
The exception to this principle (not rule) is the use of vulgar intensifiers.
They only intensify, but do not suggest a positive or negative.
Boy, what a fxxxing beautiful sight! (intensifies only)
Boy, you don't know fxxxing jack-shit! (intensifies only)