Although all offences might be equally illegal if you treat illegality as a legal / illegal dichotomy, if you take a broader view of the whole process, all offences are not equal. At least, that seems to be the essence of the complaint that cyclist deaths are not treated seriously. Sure, it's illegal to run down a cyclist but in its application - its prosecution and sentencing - the criminal justice system says that killing a cyclist with your car is not as illegal as, say, burning down a furniture shop.
I don't think you forfeit the right to complain about other infringements just because you infringe some laws yourself. If, for instance, the police are singling out cyclists because they are slow and relatively easy to stop but ignoring the infringements of motorists because they are fast and following them up would involve a lot of effort, you have a legitimate complaint that they are picking on soft targets rather than going after people with much greater potential to cause harm.
You can't complain just about getting caught but it is still reasonable to ask why your actions are illegal, to question how you were caught and why the police have chosen to enforce one law and not another.
For the record, I cheerfully cycle on little bits of pavement near the office in the morning (around 7.30am) when it's quiet. When I have Ellen on her tagalong or in her trailer, I unapologetically cycle on miles of pavement. Always with consideration for pedestrians, of course.