I am thoroughly confused..
Well, let me try an effort to make it clearer to you. Although I have the feeling I am starting to repeat myself and someone else might be better capable to explain this very common principle.
In a discussion each person has an equal level of validity.
Keep in mind that I said; in a discussion (a conversation, a dialogue, an exchange of thoughts and ideas by word of mouth or through writing).
That is the starting point.
It is like horse-racing, all horses start from the same line and run the same distance. One might be better, faster, healthier, younger or more experienced then the other, it makes no difference. The running distance stays the same. The starting point stays the same.
Saying that the level of validity is equal or that each person is equal in a discussion is not the same as saying that all opinions are correct. Or worthwhile. Or encouraging. Or wise.
It is during the dialogue that we find out through examining the argumentation which argument is valid in supporting a particular opinion and which argument is invalid.
Someone may not like a particular opinion, not listen to a particular opinion, see a particular opinion as untrue. That is fine. In a dialogue all these things do not matter. You engage into the dialogue and then the principles of dialogue apply.
If we were to apply this to horse-racing then my point is that all horses, no matter what, are considered equal and start from the same starting-point.
If you look at the arguments of some the posts here on this thread you will see that some are of the opinion that a particular horse is better then the others and should therefore be given a head-start. Or better still, bring him to the finish-line before the race so we all know in advance which horse is the best.
Hope this cleared the confusion a bit...