There is nothing wrong with singing about local sides that see themselves as rivals, nothing wrong with talking about them.
As SJ said, the problem comes when you judge your own clubs success on how you have performed in comparison to them.
We no longer do this, nobody saw last season as a success because we finished higher than the fewers.
we are now looking upwards and focussing on that, they are watching our rear ends disappear into the distance and desperately trying to keep up.