There is nothing wrong with questions that solicit opinion, debate, arguments, polling, or extended discussion, if you want a forum; Stack Exchange sites are not forums, and those types of questions just reduce the usefulness of a Stack Exchange site (generally speaking).
What is the usefulness of a question where users express their opinion? What could future readers find useful in that question? If the question involve expertise, then it can be more helpful, but for opinions there are already many available forums. (I am not saying that forums are not useful, but that is not the target chosen from Stack Exchange.)
Such questions tend to have a possible infinite number of answers, as every user could have a different opinion, and questions were there are more than X answers are not very helpful. Look at the questions on Meta Stack Overflow where the answers are more than 50: As the answers are not visible on a single page, most of the users would not read all the answers.
I think that the description used for that closing reason is clear enough to let users understand why the question has been closed. In the case that is not clear enough, the FAQ should help in understanding that.