I rather like the notion that Winn really could have handled the negotiations herself, but wanted Bareil out of the picture for good.
I think it's very dangerous for one culture to say that its values are "better" than another's, regardless of how "universal" it may be. Additionally, if you think the Federation should do something about it, what would you have them do? Simply say, "Oh that's wrong!" and move on?
As we don't know what may have led to Ferengi society forming the way it did, I don't think we're in any position to objectively judge them. Not saying we have to approve, but I have a pretty good idea how humans would feel if an alien race came along one day and told us all the ways in which we were doing things wrong.