I think being butthurt over the ending of ME3 is as disreputable as being a fan of the game. After all the butthurt comes from people feeling let down by a game they once loved.
I don't think you have to love something to be irritated by something being hugely inconsistent or just mediocre. I mean, film critics don't have to love David Lynch's older films to criticize his newer ones, as a quick example.
I'm not really talking about people who thought the ending was artistically flawed; I don't think butthurt and criticism are the same thing. To my mind, criticism is a reasoned evaluation of the merits of a given work which aspires to be universal while butthurt is the sensation of being personally wronged due to an emotional to the work. The generic ME3 butthurt I'm thinking of isn't really criticism of it for its artistic mediocrity, but anger for its failure to provide them with what they see as the epic story of their particular Shepherd.