Discussions can be based on opinions or facts, as one persons fact can "appear" to be an opinion by another person who has not had the same experience. That being said, discussions should occur, and they should be directed at things, events, or even behaviors, but never at people.
Once it gets personal, it turns into an argument.
If you feel the need to call someone out, do it in a PM. Otherwise, keep discussion threads non-personal.
We're all going to disagree, but we can disagree without calling names, making light of, or otherwise making someone feel insignificant.