Even in democracies, the law is abused by those in power. I distinctly remember one party here in germany, slowing down criminal processes of member of the oppossing parties, so that there trials could be held during the election campaigns.
Everyone has an agenda. People in power will generally (ab)use it at some point, e.g. to help a friend.
Absolutely. That's human nature. The differences: there are due process, separation of power and free speech in democracies.