I hope people don't give the 'do you know who I am' comments, I haven't seen any personally and I spend way too much time on here.
I don't buy that some people's opinions aren't more valid than others. We all have the right to have an opinion, and we all have the right to challenge opinions. Some people are simply more knowledgeable, experienced, even experts in certain topics. I guess this comes down to this question, "Is a messageboard a method of providing everyone with an equal voice, or is it a method of learning from others". People on here have very different experiences, education, knowledge, expertise, training, culture, character. It's fine to debate, it's what it's for, it's fine to listen and learn too, and far too many people aren't prepared to do that. Too many people thinking the knowledge they have attained in their life so far is enough to make them an expert on a topic, and anything they don't know isn't worth knowing. This give rise to a closed down and intellectually dishonest interaction. Then personality takes over as some people revert to abuse, and others retaliate and it decends.
I guess we all need to try and approach discussions with a bit of an attitude to listen to counter arguments, without taking it as a personal insult.