The phrase "passion on both sides" means that both parties involved in a situation or conflict feel strong emotions or intense feelings about it. Full definition
Outside of perhaps sports fans, I can't think of any medium that brings out passion on any side of a given property quite like gaming. (thegamefreakshow.com)
What is it about sequels which inspires such passion on both sides? (cubedgamers.com)
There is passion on both sides as each side puts forth their arguments. (quixoteslaststand.com)