I don't believe that for a second. People get into policing for all kinds of reasons. But the common denominator is that the barrier to entry is very low these days, and they expect to be hiring people with intelligence below a certain level. It has been explicitly stated as such by a number of police departments around the country.
When your entire workforce is filled with grunts just following orders they don't generally have the best critical thinking skills.
Are there some people who get into it for the reason you mentioned, probably. But, if you think everybody joining the police is doing it for that reason, you're sorely mistaken.