If he gives you any guff remind him that the Bulls still suck and have been as bad of a franchise as the kings for the last 20 years. If the kings and Bulls switched conferences they would be 30-52 and the Kings would be in the playoffs.
Or, ya know, negative thoughts are a naturally occurring byproduct of being human? And orienting oneself toward positivity at all times may have toxic consequences of its own? And instead it might be wise to learn how to regulate all of our emotional responses to our circumstances, rather than cut ourselves off from fundamental emotional experiences?