…between having an opinion and being dogmatic…
In the past, I’d been occasionally complimented (?) by some people that I didn’t impose my own tastes onto others (meaning, not having strong preferences, which kind of prompted me to to write this). But in reality, I do have opinions on a lot of stuff (maybe not as much as some). It’s just that I feel that arguing over it isn’t important and useful most of the times.
I don’t consider having an opinion a “bad” thing. Actually, I consider having an opinion an inevitable human (or somewhat like a biological) thing. Of course, one can argue that it matters whether it is of one’s own or just plained borrowed (meaning, without “verification” with one’s own judgment). If you don’t have your own reasons for stating a particular opinion, I don’t think you can consider it as your own, and I don’t think you have any grounds for stating and supporting it.
The bigger issue is figuring out when having an opinion becomes dogmatic. I meant by “dogmatic”, roughly, being unwilling to listen to different views from one’s own. Often, this results in illogical, emotional and personal attacks on the other parties during a debate or a discussion. I believe this is one of the most destructive state for a society (however, I am not saying that it’s unnecessary at all. Emotion brings out action, and that would be a different subject).
But on the other hand, you can’t just be quiet either sometimes! You’ll have to decided how far you are willing to push your opinion (partly depending on what you think of the other (conflicting) opinions).
What makes it more difficult is that deciding when it went too far is also very subjective. Within a homogeneous group or a society, it might be easier, but still each individual of the group has slightly different ideas about the same thing (emotionally, intellectually, ethically, etc.).
Again, this mumbling seems to go anywhere specific… 
Anyway, all this reminds me that the communication is the most important thing. It’s not like one’s opinions never change…