The number of leaf fans who didn't like Sundin, over the course of his career, is small. Near the end of his career things were different, but they felt the team needed to change direction, rebuild, and he was the best trade chip the team had and his age prevented him from being a long term player. Since he didn't want to give up his no trade clause, alot of fans were bothered by it. But that just goes to show no player is above the the welfare of the team. I for one felt the same way with Bosh. I always felt he was overrated and overpaid, but a very talented player and deserving all-star none the less. Yet when he turned down the contract extension I thought it was in the best interest of the team to trade him. I could care less that he was a reliable 20 and 10, that he had been the best player on the team for 5 years.... his trade value was at its maximum, he wasn't a franchise player and there was no guarantees he was sticking around long term. I heard it out the wazoo how I wasn't a 'real fan', that I didn't understand basketball etc etc.
There are no doubt fans who dislike a player, or will always dislike a player, for whatever reason they have. I'm not sure expecting 100% support of a player (any player) is realistic or reasonable. If Bargnani turns it around I guarantee the vast majority of fans will be supportive and excited about him. Will some not? ofcourse. But they will be few and far between.... and I don't think anyone should expect everyone to have the same opinion, view, level of support, or whatever, of a player. Having dissenting or critical views is not a bad thing. It at the very least keeps everyone on their toes.