mentsch: The exact same event IS set up in Israel by the kever of Shimon bar Yochai by many [real] Breslev Chasidim, and it does not descend into the same madness. The part of Breslev that insists on Uman also seems to also be the part that attracts tens of thousands of hippies.
The “idea” of going to kevrei tzadikkim at this time of the year (Erev Rosh HaShanah at least) is brought down in the Rema, so I would not recommend calling it kefira.
The disaster of Uman is not just because of people going to a Rabbi’s grave. That happened for centuries with no problems. The disaster is because of a group using hippie, feel-good yiddishkeit as their selling point with no concern for the consequences.