A common theme I see to support the ideology of "GM supremacy" is the fact that it shortens arguments or simply makes resolution conflict easier. This same idea applied to a Roman Emperor, did it not? During times of war or civil unrest, the Republic was turned into a totalitarian oligarchy with a single, central leader? 

Each situation and scenario is going to be different. At times, the word of a GM being law not only opens up the system to abuse, but allows for toxic and detrimental decisions. If the system was so inherently perfect that every GM that abused their power would have unpopular roleplays, then you would never see them around - at least, not for very long. Yet, I'm almost sure that everyone here knows of at least one thriving or living roleplay with notably abusive GM's.

I believe, in essence, that there deserves to be a checks and balances system. Even if a GM creates every aspect of a roleplay, they did so to interact with others. The existential purpose of a roleplay is to have others in it, and with that said I believe that at some point a GM and a roleplayer should be considered equally important, just as that GM may be a roleplayer in a different roleplay. The idea that each GM is god within their domain is great for the sake of simplicity, but ideally a system to diminish that mentality so that a GM will always be given a sense of sympathy and incentive for a roleplayer would yield a far healthier community. If a GM makes a mistake or has a flaw and it interferes drastically with the work of a roleplayer, it is best to compromise instead of demand alteration.

If we lived in a world where most people weren't egocentric tits, not having a system of checks and balances wouldn't have a purpose, but it could really serve a good one and most likely help in a more advanced, healthy atmosphere. It would never hurt to have a set of 'basic human rights' for roleplayers to insure fair treatment, or a method of definitive compromise.

[quote]someone criticising your role-playing skills isn't like someone walking in on you during a single-player game and criticising your skills,[/quote]

Opinions are not universal. Even if a majority shared an opinion, that does not mean they should get to dictate the literary art flow of another. In a situation where stylistic techniques conflict so greatly that one party does not wish to engage in roleplay if they cannot use at least a certain degree of their style and another one cannot tolerate that minimal degree, then one party should simply leave,.This is different in essentially every case. It could end up being a question of whom is the more healthy individual for the roleplay, whom is more skilled, whose style is better suited or just plain whom has more friends in that active community. However, most of the time, making polite requests instead of critique is a far better method of solving this error. Instead of saying, "to improve this aspect of your writing/roleplay/debate/painting/sketch, you should do X" simply saying "I have difficulties following your lengthy sentence structure, could you please avoid run on sentences?" or "I would be more comfortable if you had less detail in your posts for now" does a far better job. If they choose to ignore those requests, then you move to more drastic measures. Thus, even if roleplay involves interaction, I find unwanted critique or criticism without permission to still be quite rude and out of place in any setting. There is no point whatsoever in actual critique, constructive or not, if it is not communicated in a healthy way to promote said constructive habits. It is, for all intents and purposes, at that point nothing more than a rude annoyance and by far from a basic right one gains simply by 'interacting' with someone.