Police work by its very nature involves the slippery slope (the potential for gradual deterioration of social-moral inhibitions and perceived sense of permissibility for deviant conduct). In fact, the whole unspoken "dark" side of criminal justice work involves putting up with conditions that are at less than usual comfort levels; ., "slumming it".
Police are routinely involved in undercover work which involves taking on false identities and inducing crime. Police are allowed to make false promises to hostage takers and kidnappers. Police feed disinformation to the media. Police are trained to be deceptive at interviewing and interrogation. Police make all kinds of excuses to get out of nuisance calls. Police trade or sell their days off and desirable work assignments. Police angle themselves into cases requiring court appearances and manipulate the overtime system to earn an average of $5000 more a year. Police strain the truth to protect loved ones and crime victims. Police routinely invade privacy via surveillance and other technological means. Police fighting the drug problem may encounter more loose cash than the gross national product of some small countries. And as with sting operations, there's something that's just plain sick about a system that condones the police making a product, selling the product, and then arresting people for buying the product.