What's wrong with a little impertinence? Seriously though, most of what you've been arguing about are just straw man arguments.
The ending(s) of ME3 are demonstrably *bad* (and by bad i mean poorly executed and unsatisfying, not that it wasn't the mega-fun happy ending or the Scooby Doo ending.) As paying customers who were promised something *good* in this regard we are within our rights to make our dissatisfaction known and it's within the interests of the game developers to pay heed. Do some fans take it too far? Sure. Welcome to the internet. But does that negate the validity of the reasonable complaints and constructive criticisms levelled at the game?
Speaking as an artist myself, I think I can safely say that artistic integrity doesn't enter into it. Art doesn't exist in a vacuum and has *always* been subject to critical and peer review, doesn't matter if it's a painting, sculpture, musical composition, feature film or video game. People have an odd idea that the artist's vision is always sacrosanct but the reality is that this is simply not the case. Never was. Art is largely done on commission, which means you're doing it because someone wants something specific and is paying you, the artist, to make it a reality. If you fail to do so, or what you produce doesn't meet the agreed upon specifications then you either don't get paid in full or you have to go away and try again. It's the same principle here. Art was commissioned. It came back as a masterpiece with a glaring flaw, akin to a red clown's nose on the Mona Lisa. Kindly go back and fix it.