Well, playing along...
The unpopular opinion PK held was that we should promote an unusual set of rules (basically, bar rules) instead of the World Standardized Rules, or BCA/WPA-type rules.
The general attitude on AZB (and I can't say I disagree) is that bar rules are made by low level players, for low level players, and would be a joke in the hands of professionals who could exploit weaknesses in these rules, weaknesses that would basically ruin games like 8 ball and lead to stalemates or blatantly unfair situations where the game is effectively unwinnable.
There was some additional backlash because it was pretty clear PK was a low level player who didn't understand the nuances and reasoning behind these rules. His status as a banger was cemented when he suggested stuff like the ram shot, scooping the cue ball to jump it, blasting balls randomly to move them away from pockets, etc.
He added multiple baffling rules to his guide that existed nowhere else on earth, such as directly hitting the 8 ball first with the cue ball = instant loss of game.
It further annoyed people because he insisted on renaming virtually every conventional term from jump shots ("air to ground shots") to diamonds ("locators") to combos ("chain shots").
So it seemed pretty conceited for a banger to say "Here is the way everyone should be playing, using easily-exploited scrubby rules, and let's all use completely new terminology. That should fix the lack of standardization in pool rules, make it more accessible and popular, and bridge the gap between amateurs and pros."
Hope that clears up why PK was so unwelcome. As for what you can do to avoid hostilities: Probably forget writing any sort of guide, erase ram shots from your memory, and if you do decide to write something, you may want to studiously avoid echoing any of the unpopular sentiments mentioned above.
