Posting courteously to mailing lists

Is it wise to always express your opinion (even if it is a harsh and stinging attack on an individual) in a public forum or a message board or blog that is read by all?

Why do people wash dirty linen in public? I have just begun subscribing to a mailing list where some mailers who post are at the other's neck. Some of them who post regularly are always ridiculing earlier posts. They are not citing any factual incorrectness, just expressing their opinions on issues on which everyone is entitled to an opinion. I wonder why this happens? We have these 'know-alls' putting the others down. Sometimes the comments are totally uncalled for.

At times, it just gets to me. I can unsubscribe but then there are people who post information and facts which are quite an awakener. So i dont want to miss those.

Reminds me of a story. A young elephant was chained by a circus man. The poor elephnat did all it could to break free, but each time, the elephant found out that the chains were too strong for him. The elephant never tried again. So when the circus man removed the chain, the elephant never moved or even tried to break free.

That old elephant reminds me of those who refuse to believe anything other than whats in their shell.

All that i think is needed is
->Respecting other opinions ( It may come from the world's biggest fool but that fool may know something we dont know, so we can learn )
->Accepting one's own weaknesses and shortcomings ( No one is perfect )