This site does not allow for duplicate questions. I note that you appear to have asked or answered this exact question several times on two accounts. You can't ask the same question multiple times, even if you disagree with the answer, without that question being closed as a duplicate.
The standard way to correct an answer you believe to be incorrect is to place your own answer to the existing question. This will not always work well since the existing accepted answer usually has a vote lead, but it's possible (even encouraged) for the asker to change the accepted answer to a new one if it's more correct.
The deleted answer of which you speak appears to have been nominated for deletion (including by Oblivious Sage, who has the accepted answer) due to your use of a rude and argumentative sentence:
There is no passage limiting DR to one damage type per attack. If you downvote without quoting such a rule you are promoting ignorance. Rule is written as intended. ANY time damage of resisted type is taken, reduce damage.
Personally, I prefer mech's approach of simply removing that sentence, but if I had to guess the moderators' reason for deletion, it's that you appear to be using the site to force through your own reading of the rules rather than the site's intended purpose of asking for and providing answers.
I do not know why your answer to this question was downvoted twice. It's good form, when downvoting an answer, to explain in a comment. It appears that this was not done
(or, if it was, moderators deleted the comments, which often happens). Your second answer was essentially a comment, and was deleted as it is not an answer to the question. The answer box is only for answers to the question.
To answer your literal question, it is most likely that the other user will not admit that they are wrong because they do not believe that they are wrong. You yourself appear to be in the same position. The case appears to be arguing over an ambigious rule, which is common in D&D and difficult to answer.
I recommend moving to D&D 5th edition and leaving this awkward edge case behind. Your miniatures will still work and you will be able to receive official rules answers on issues like this by asking Jeremy Crawford and Mike Mearls on Twitter.
Addendum: The user's entire post history on two accounts, which appears to be entirely arguing over this point: