Hasidic Proteksia?

Whoever comes to my gravesite and recites the Ten Psalms of the Tikkun K'lali ('General Remedy'), and gives even as little as a penny to charity for my sake, then, no matter how serious his sins may be, I will do everything in my power -- spanning the length and breadth of Creation -- to cleanse and protect him. By his very payos ('sidecurls') I will pull him out of Gehenna (purgatory)!
(Rabbi Nachman's Wisdom #141).

I believe with perfect faith tha G-d rewards those who keep His commandments, and punishes those who transgress Him.
(The Rambam's 13 principles of Jewish Faith #11)

Can both #141 and #11 be true? Surely not. Either God punishes and rewards, each according to his deeds, or Rav Nachman provides a bit of Proteksia for people with payos who make the long trip to his grave in Brestlav.

Maybe I have an acute sense of justice, but Rav Nachman's promise offends me. The guy who gives a penny in Brestlav isn't entitled to special treatment; he should be judged according to the same set of rules that govern the rest of us. If favored treatment is available for Rav Nachman's believers, the whole system breaks down. In fact, if there is anything to Rav Nachman's promise, why keep any mitzvos at all? Let's spend our lives mudering, fornicating and desecrating Shabbos. So long as we make it to Rav Nachman's grave before the STDs or the next-of-kin catch up with us, all will be well.

Anyway, we believe that God's system of justice is self-sustaining: Reward comes as a direct result of our actions. When good things happen to us, it isn't a sign of God's favor, but a natural consequence of the things we do. Just like STDs, in fact. The technical term for how we always reap what we sow is mida k'neged mida, and it is very hard to see how Rav Nachman's promise honors that principle.