1. It is not as simple as that... even if speed itself is not the cause of an accident, or if the accident is the other party's fault, the higher your speed the worst off you, your passengers, and the occupants of the other car will be.... obviously no one is suggesting that cars should only travel at 10mph, but a balance need to be struck. And while we could debate if the limit should be set at 70mph or 100mph, there is no doubt that 160mph is inappropriate for public roads and poses unjustified risk to the travelling public...
2. While police are entitled to break the law when it comes to traffic, they still pose a risk. The risk is minimised by ensuring that Police drivers are properly trained and have good vehicles, but it is still there. This is why Police cars should only break the law when absolutely necessary to do so. Any case where this is done without due cause is potentially putting motorists at unnecessary risk.