No, it's not.
If you have suffered something that you think is a crime, call the cops (in the UK they are pretty okay for these things).
If you had a very bad experience, but maybe not a full blown crime, you might decide to make a 1.0 star rating and complain to the company.
There could be systemic problems (racial discrimination), but even in those cases, there are concrete victims, that can report it to authorities (to the TfL for example).