^Even a democratic society can get imperious in its treatment of others, as many, many Second and Third World "beneficiaries" of American intervention could tell you. It's not good to have one unilateral superpower, no matter how benevolent it may believe itself to be.
The United States' consistent inability (and in many cases) unwillingness to live up to many of its own stated doctrines from the founding of said nation onward points this out but, however, I'm not sure a rival superpower makes things any better. Rival nations (France and Britain, the Germans and British, the Ottomons and Hungary) seem to bring out the worst in each other as opposed to the opposite.
In addition to the threat of MAD, the Typhon Pact are just as likely to make the Federation worse as the Klingon Empire did Kirk's era.
Then again, I'm not the writer. I'm just a fan.