When selecting the Unstoppable Momentum skill modifier for Bleeding Edge, any +damage effects on the player weapon are removed from the skill completely. They are not subject to the -38% damage modifier from Unstoppable Momentum; they are just completely removed. This includes:

+damage modifiers rolled on the weapon itself, regardless of damage type.
+damage modifiers applied to the weapon through sockets, regardless of damage type.

This is causing enormous amounts of lost damage, but is also causing issues where Unstoppable Momentum cannot be successfully used to apply ailments of choice as entire damage types are completely removed.