Actually I got just the opposite feeling from Erathis. For her, order is paramount. Erathis supports law/civilization/order regardless of tyranny.
Bahamut and Erathis share the justice domain.
Divine power states:
"Bahamut sees justice as the tool of good intentions. Laws and honor exist to protect those who cannot protect themselves and to prevent those who wield power from taking the path of evil."
and:
"Erathis views justice as the driving force behind civilization. Without law...society dissolves into chaos."
Additionally you can look at The Plane Above for Erathis's "game of making," which is an attempt to rebuild the lattice of heaven through mastery over creation. The good gods (e.g. Pelor) know that Erathis intends to carry out or have her followers carry out a variety of evil/depraved experiments to further the advance of creation. For that reason they are unwilling to particpate fully. For her part, the rebuilding of the lattice of heaven and the restoration of order in the Astral Sea justifies these actions.*
I'm pretty sure that a follower of Erathis would thus view a follower of Bahmut as naive, idealistic and too willing to sacrifice order for the sake of, "good." Much of what Bahamut would see as intolerable tyranny would be acceptable for Erathis given the importance of battling chaos. The priest would likely mock the character for not having the stomach to do what is necessary to fight entropy.
*I can't find the quote but somewhere I read that Erathis views tyranny as simply, "one possible form of civilization," and thus acceptable and within her sphere (she butts heads with Asmodeus over this.)