In my book there is a big difference between disagreeing with someone and calling them names. The first can be helpful -- if you tell me that using fluoride, for instance, is a great thing to do for your health, I might disagree with you in the form of saying, "Wait -- here is what I have learned about fluoride that indicates it is not in fact so great for us!" The second, where I say "PBuddy, you are a loser because you believe that!" is not only unhelpful but hurtful. We all know that difference and it's important to keep it in mind everywhere in our lives, whether we are person to person or anonymous to the degree that we are here.
A good rule of thumb for me is to try to stick to my experience and knowledge (with the understanding that I don't know everything!). When a post reflects one's feelings or opinions, that is when ego, rather than a spirit of service, is involved -- and it's when things can get ugly.