Couple thoughts. .. Probably best to think of the Gestapo as analogous to the FBI, a federal law enforcement organization that dealt primarily in domestic national security cases. The FBI was probably more processional, but only by degrees. In both cases they had small local offices in most areas, but their strength lay in their national organization and the resources they could call in if needed. Most nations have an organization like this and most of them have a questionable human rights record. The phenomenon is not limited to Nazi Germany, but rather what happens when humans are given power without accountability, especially when they feel they are working for the greater good. Power + purpose - accountability =abuse.
Why go to all the trouble? All it takes is a cop saying "either you move or you go to jail". It doesn't matter if there is real grounds for arrest or not, or if the case will get thrown out whenever it gets before a judge, a police officer can put you in jail and cost you hundreds, if not thousands, of dollars in bail. Yes, you will probably eventually be exonerated, but in the mean time... I was thinking about this today after my last post (probably thinking too hard, I missed two turns on the way back ) and a police officer's job is not just to enforce the law, but also to keep the peace. It has long been recognized that laws cannot anticipate every situation and because of this, those who enforce the law are given a significant amount of discretion in how they do so. On the one hand, this shows up as giving a speeder a warning or choosing not to arrest a homeless person for something minor, but it also can be threatening someone with arrest even though no crime has yet been committed because if things keep going the way they are someone is going to get hurt. Up to a point, most people would say that this not an abuse of power, but rather a reasonable use of it to prevent problems rather than waiting for an actual crime to happen. Short version is that police officers need a certain amount of discretion in order to do their jobs, and a big part of that is to be allowed to overlook some crimes and to act in some cases where an actual crime has not yet happened in order to keep the peace. Where this becomes problematic is when there is a lack of accountability. When a badge becomes a license to play god and the discretion granted is not backed up by oversight, then abuses will happen. This is not because cops are bad people, but because they are human and when people are put in a position of power without being accountable then abuses will happen. Getting back to the Gestapo, a lot of their problems, and those of other national police forces, stem from the first term. Gestapo is an acronym for Gehime Statz Politzi or Secret State Police. While an element of secrecy is probably necessary to the operation of a modern government, and can be critical during investigations, secrecy is the opposite of accountability. If no one knows what you're doing, then by definition you are not accountable and therefore in a situation that practically guarantees abuses.
When Hitler first came into power, there were two high ranking and powerful Generals that could actually stand in the way of his eventual ambitions. In order to dispose of them, there were actions taken in order to remove them from power. These actions needed to threaten the Generals with enough exposure as to discredit them entirely. In one case, the General had married a prostitute. https://en.wikipedia.org/wiki/Blomberg–Fritsch_Affair http://www.historynet.com/the-blomberg-sex-scandal-march-99-world-war-ii-feature.htm They threatened to go public with this information unless the General resigned. Rather than face this scrutiny, the General did resign. In the second case, they were able to plant evidence of homosexual encounters so that the General had to resign to avoid further action which was being typically carried out against homosexuals at the time. Once these Generals were no longer able to thwart Hitler's future plans, the regime no longer had any major opposition within the army. Until these actions were taken, Hitler had been quite stymied. All it took was a few acts of character assassination to counter act successfully.
