Anyone who thinks referees are completely unbiased in their calls knows nothing about science.
Consider the famous "gorilla experiment" where the man in a gorilla suit is not noticed by 50% of the observers when he walks across the stage, when they are told to concentrate on something else happening on stage. Consider that eye-witness accounts are considered to be mostly unreliable now in court cases.
We all have our biases. As RU fans we certainly don't see the referees' calls accurately, as we expect to see our team do better. We are undoubtedly more biased than the refs, but they are far from immune to the foibles of human perception.
Referees are human. They go out there knowing which team is expected to be better, and that is going to influence their perception of what is happening on the court. Some referees are better able to adjust than others and so seem to be fairer, but there is no person in this world that is able to see such things with an unbiased eye. It is what it is.