Heh, an interesting group of points, Marfig.
I, for one, do not believe that all beer need be pasteurized, and actually it would greatly affect the flavor of the final product. HOWEVER - that doesn't mean it's a bad thing! Different beers need to maintain differing levels of yeast to maintain or enrich their taste.
For instance, many of the Trappist and Abbey breweries in Belgium do not ever pasteurize their beers - either on draft or in bottles. The reason is because the beer that is shipped is expected to further ferment within the vessel, and "ages" much like a fine wine. Killing the yeast would actually cause these beers to taste unfinished and overly saccharine as the sugars would not be properly decomposed.
On the other hand, a beer that does not specifically require active cultures could end up tasting awful if they are left after the bottling process, for the exact same reason - the sugars could become overprocessed, leaving a bitter, metallic taste that you can tell instantly is not the result of the Hops. The beer goes, in a word, "skunky."
As such, I look at pasteurization as a tool that helps a beer maker control and refine the craft further by stopping fermentation at the desired points, not simply a preservation method. In most craft beers, the preservation should be handled by the addition of the Hops to begin with, but milder beers require that you not add a large degree of them and thus you need other methods to stagnate the yeast and prevent fermentation past the desired point. These beers would not even be possible (or at least commercially viable) without pasteurization.
So, like all things, I think pasteurization should be viewed in moderate light - there are places it's required, there are places it's convenient, and there are places it is undesirable.
And for any purist who truly whines about it, the same beers that are pasteurized in bottle are also hit before the keg, I think! You'd be limiting your palate to only some of your closest microbrews (that don't ship nationally) and specific national/international beers that maintain the yeast for a reason. What a shame to deny yourself so many other great beers simply based on what should, for all intents and purposes, be considered a tool in the process the same way as the fermentation is!