In the "old days", fans cheered for their team, and were mildly excited when their team beat a rival.
These days, fans become so arrogant that they sometimes root harder for another team to lose then their own team to win, mostly because they want to see the other teams fans suffer.
It's a long road as to how this developed, but it has been amplified by talk radio which allows the blow hard fan airtime.
For example, I am a Mets fan. I have been since the late '60s. Mostly because everyone in my family was either Red Sox or Yankees and I wanted to be different. Through the years, the Mets have been up and down. However, around here, the local Yankee fans used to "beat on me" in the local pubs and stuff when they found I was a Mets fan. Sure, the Mets sucked, but why should that matter to them.
These days, I internally gloat, but always tell them "don't worry. The Yankees are always there at the end of the year". HA!