Would you rather Blazers fans were saying "it sucked rooting for him, good luck with that, you're going to hate him"?Why is the generalized opinion of another fan base relevant to how much he can help the Celtics? There are better ways to measure a player.
More seriously, it isn't relevant to how much he can help the Celtics. It IS relevant to how much Celtics FANS might or might not enjoy watching him play.