Well, it certainly should be to the GM. Why else do we have one? But that wasn´t your question, right?
I think the answer, as always, is "it depends".
Generally, I think it´s disrespectful and undermines the integrity of the game to settle for mediocrity. Disrespectful to your opponents, to the officials, and to the history of the sport. There were players in this league who shed blood to win a title, and you´re certainly not above that.
Let me put it this way: Red wasn´t lighting up cigars for good effort. And little KG didn´t grow up and said "Momma, I´m going to become a professional basketball player, and I will play .500 ball for my entire career."
Now, if you´re a young team, and nobody can realistically expect you to win a championship, then of course I´m more forgiving, but I still expect you to give your best to win a title one day. If you´re a super talented rookie and all you look for is a quick paycheck and blonde women, I will be angry and certainly never root for you, precisely because you´re disrespecting the game.
I mean, what´s next? Allow PED´s, because they enhance the physical capabilities of players, and thus the spectacle?
I despise Lance Armstrong, and I don´t give a dang about the "incredible story" he´s selling us. All it does is leave me with a shallow feeling.
The art of basketball, and what Red taught all of us, is as much about winning, about your team vs my team, than it is about a perfect form in your shot or setting a pick. If you can´t oblige to that, I will forgive you. If you don´t care about it, get out of my sight and don´t you dare to ever come back.
On a related note, and maybe I shouldn´t bring that up, but I think most of you who say winning doesn´t matter on whether you root for a player or not are lying to yourself. Back when I organized the "25 greatest Celtics of all time" polls, we all collectively voted for KG before the likes of Ricky Davis, Dana Barros and Antoine Walker, even though he was only a Celtic for two years. The obvious reason for this is that winning does matter to us, and that it plays an integral part in who we consider to be "a real Celtic".
Finally, I want you to watch this:
Seriously, even if you´ve seen it before, watch the whole 10 minutes, and don´t skip the part about the Timberwolves.
If you´re a fan of Kevin Garnett, what exactly are you a fan of if not winning?