I’ve found that is very easy to travel down the path of personal opinion which does not make for a great research topic; in fact it makes for a rather lousy one. However, opinions are not all bad; they can start a rousing conversation or brainstorming session.  An opinion can also be the foundation for a research topic that will either prove or disprove the beliefs behind the opinion if it is addressed objectively and without bias. Understanding why you have the opinion or belief you do at a deep level is a great achievement.