This is not a defense of Nick Diaz.
Nick Diaz broke the rules and now he has to face whatever punishment is meted out by his employer and the Nevada State Athletic Commission. I leave the debate over what that punishment should be to a dozen other posts, and thousands of other vitriolic comments.
What this is, is a defense of basic logic, and the hopefully noncontroversial premise that words have meanings that should be respected.
First, let's break down the deductive method behind the belief that Nick cheated by using marijuana:
1) Using marijuana is against the rules
2) Violating the rules is cheating
3) Nick Diaz used marijuana
4) Nick Diaz cheated
The process of that deduction is fine, but the outcome is wrong, because one of the premises -- 2) violating the rules is cheating -- is demonstrably incorrect.
So let's talk about that premise. I've looked up cheating in every dictionary I can get my hands on, and the primary definition is, universally, some variation of the following:
"Act dishonestly to gain an advantage, esp. in a game or examination: 'she cheats at cards.'"
In all cases, the primary definition of cheating focuses around an act of deception intended to defraud or deprive another person out of something of value. Without the intent to gain an unfair advantage, the dishonest act itself is not enough to constitute cheating. So unless you can make a case that Nick Diaz smoked marijuana to gain an advantage over his opponents (and I'd be interested in seeing that logical process unfold) you can't make the case that he cheated.
So let's go back to that second premise: 2) violating the rules is cheating. It fails its own deduction.
Both of the following premises are correct
1) all rules prohibit cheating
2) some rules prohibit things that are not cheating
3) While all cheating is rule breaking, not all rule breaking is cheating
Nick Diaz violated the rules, but he didn't cheat, and that's not just semantics. His actions are missing a critical element of willful, purposeful deception that makes cheating so odious in sport. He should be judged for his rule violations, but not against the standard of cheaters.