There is a difference between the behavior of the two parties. Your argument does not square with the facts. Contrast what just happened in New Jersey with what is happening in Wisconsin, Michigan, North Carolina, and elsewhere. When conservatives are about to lose power, they change the rules to disempower the Democrats coming into office. But in New Jersey, where some Democrats moved to take the same approach with their state government, it was liberal activists who fought against the proposal that would ultimately benefit many of their causes. While it is true that many liberals might be upset and vent their spleens, when it comes to making policy, the Democrats act fairly when the Republicans cheat.