I think you'd see a variety of political arguments against this that would amount to such an action helping terrorism, those supporting it are trying to undermine America's security, or that placing the fear of prison over an officer's actions amongst the force would prevent them from doing their job properly.
>Otherwise upstanding policemen are being pushing into violating the law by their superiors
They already are in many ways. There were leaks from the NYPD where the officers involved exposed that they were subject to mandatory stop-and-frisk quotas and that racial profiling was highly used in doing so. Likewise, drug busts provide huge income to local police forces [1]. There is therefore an incentive to bend the law because it brings their force income, getting these busts looks good on an officer's record and having a cash flush precinct means there won't be any holding back on giving out overtime.
1. http://www.wfsb.com/story/22078253/what-happens-to-all-the-m...