I totally disagree. Policemen put themselves in harms way, I am happy for the law to offer them a little extra protection - especially in the UK where most of them are unarmed, so can't protect themselves any better than civilians who don't take extra risks for my sake.
Edit: actually, it's more than that. For our society to work, people need to respect the police. If you can hurt them with the same risk as killing anyone else, then we are all more exposed to danger because the police will have less real authority to protect us. So yes, pursue those who attack the police more vigorously than those who attack civilians.