Since I saw the ruling that said if a personality was gaining 2 honor and was dishonored and facing a Shiro Chugo deck and the Shiro Chugo player lowered the honor gain by 2, the dishonored player would still rehonor, then could I buy a courtier aligned with my clan with a base 0 PH for full and activate Destructive Priorities?
Destructive Priorities
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Since I saw the ruling that said if a personality was gaining 2 honor and was dishonored and facing a Shiro Chugo deck and the Shiro Chugo player lowered the honor gain by 2, the dishonored player would still rehonor, then could I buy a courtier aligned with my clan with a base 0 PH for full and activate Destructive Priorities?
No, that's quite a different situation.
The reason the rehonoring still occurs in the example you gave is that rehonoring is substituted for the gain BEFORE Shiro Chugo has the chance to reduce it.
But a gain of 0 still = not a gain. So, gaining 0 Honor will not trigger Reactions such as Destructive Priorities'.