Essentially, should a person make a report on a Raid Lead for something like this, it boils down to the ideology of the GM itself, like the example OhieMitzen gave. Sure maybe the GM that read his Ticket realized "okay, the guy is obviously clueless and doesn't know much about the game, let's not be too harsh on him", but I imagine you could also have a straight polar opposite of a GM reacting in form of "Right, Spellpower on Hunters, we aren't in Classic, good joke, see you in 30 days.".
There is no hard text to look up on whether "Spirit is a priority stat for healers" or "Plates can roll on Leather". Nowadays the rule itself is as inconsistent as the game-knowledge of each player (including GM). Some cases are more obvious than others, for instance literally all BiS Lists for plates including several Leather pieces, but some can be up in the air sometimes. Most common examples are "is DBW for ret?" and "is Spirit for DPS?"
But I personally believe this isn't what the "Ninja Rule" has been initially laid out for. I always believed the Ninja-looting rule was strictly made to counteract people stealing loot from an obviously rightful winner, like if the Raid Leader goes offline or disbands the raid after looting DBW HC.
But nowadays when people don't get every item that dropped, they lash out and look for any reason to get the responsible person banned, because if they can't get the satisfaction from loot, they'll get it from potentially getting the person banned. What's the worst that could happen? Getting a "no"?
Without any feedback on these cases from Staff, it always becomes irritating to lead a raid and then have Mr. Retadin call you a "massive ******" for not letting him roll on DBW and that he "will report you, so have fun playing in 60 days again." and not being 100% sure that you won't really get banned by an unlucky GM.
Pretty much agree with everything. The underlined bit gets right to the heart of what I think is the main point here.

Raid leaders that accord loot based on convictions about what item is better for what class, even if they make imperfect decisions, don't deserve to be lumped into the same basket as ninja-looters that straight up steal items. In the first place, being allowed the chance to get a raid leader banned for 60 days - if you take the right screenshots that contain just the info necessary towards your goal but omit all other context - is not a blizz-like aspect of pugging at all. It's pretty exasperating seeing some of the players that most vocally hold this threat over raid leaders' heads, like some kind of ultimate power, being absolutely abysmal players that would be much better off if they channeled some of that energy and enthusiasm over being able to get someone banned into actually learning a thing or two about their class.

Some of the posts in this thread also exemplify why it's a bad idea to let the community play the jury and try and gauge whether a ninja-loot incident occurred based on how well think one class can use a piece of gear compared to another class (like the person making spirit out to be worthless for Disc Priests).