The problem has never been what you or any other member was saying. The problem has always been the way it was said. Let us look at some examples with a right and a wrong challenge to the post.
Example 1: Someone claims that he has to hold back to avoid getting DQed in a competition.
Wrong Response: How would you know since you have never been disqualified in a competition, silly juvenile LARPer.
Right Response: How many competitions have you been DQed from? I have found that using a lot of power tends to help me in competition. Maybe you just need to try again.
Example 2: I am developing my own martial art involving (fill in the blank).
Wrong Response: You don't know anything about it, how can you make an art about it? A real art is (XYZ) not this fantasy you are calling an art and then claiming is effective even though you have probably never been in a fight.
Right Response: How do you over come problems such as this, that and the third? Have you heard of or studied any (XYZ) art, it is very similar? Do you think that the techniques in your art are such that you could defend yourself with them?
Example 3: I'm a samurai!
Wrong Response: The samurai died out years ago. You aren't a samurai, you are a LARPer. You might want to grow up and get a clue. Once you have done the research I have done you will see why this is a stupid and childish thing to say.
Right Response: The samurai died out years ago. Do you mean that you idolize the samurai of stories and movies? You can find some information about what real samurai are like here.
So what is the common thread in the "Wrong Responses":
1. They are combative in nature instead of persuasive in nature.
2. They make assumptions about what the person means instead of asking questions to resolve an inconsistency or other source of confusion.
3. They claim superiority and do not make an attempt to back up the claim or attempt to educate the original poster.
Keep in mind that most communication in person is not the specific words, but rather the inflection, tone and body language of a person. On an internet forum we loose all of these important aspects so it is even more important to read carefully and resolve any sources of confusion well before deciding to get into a debate. Assumptions in personal communications are bad, assumptions in text only communications are worse.
I'm going to finish is novel of a post with a few guidelines to better more respectful posting:
1. If there is something that seems childish, wrong, absurd, etc. ask for clarification before assuming that the poster is childish wrong or absurd.
2. Once you determine that there is a disagreement between your ideas and someone else's, determine the root of the disagreement.
3. Be persuasive, not combative. Post as if you are trying to convince the other person to see your way, not as if you are trying to make other forum readers see your way.
4. Number 3 is worth saying again: Be persuasive, not combative. At the end of a disagreement that you win, the person you debated against should see and accept your side.
5. If someone says something that is contradictory to things you know for sure, query about the contradiction while citing your original source. If it is from your instructor, give a bit of background about your instructor. If it is from a book, state the title of the book. If it is from a website, provide a link to the website.
6. Don't be afraid to 'lose' an argument. It may be that you had some bad information. It may be that you were just flat out wrong. However, by losing an argument, you are now more informed about a topic that interests you. So the defeat is really a victory.
Happy posting...
And thanks for making me work on Christmas Eve... jeez you guys suck.

(that's a joke)