thinking about this, I think he is confusing a couple of issues... it is true that police have some immunity to claims made by those who are injured by police while performing their duties... but there are limits... gross negligence would not be protected...
but more importantly, police do owe duties to innocent bystanders, and can be sued for simple negligence, not just gross negligence (more reckless than plain negligence)...
in short, an injured "wrongdoer" would have to prove gross negligence... while an innocent person, not the target of police action, could sue police for simple negligence.