Canonizing him will kill any chance of reunion with the East. The Ustashe ran the third largest extermination camp in Europe during WW II, targeting not Jews, but Orthodox Christian Serbs, and we Orthodox regard Stapnic as having been complicit. Canonizing him will destroy any residual good feelings we have for the Latins left over from the Pontificate of Benedict XVI (uniformly regarded by us Orthodox Christians as the best Pope of Rome since the Latin schism from the Church).