PSA: Having a bad KDA does not invalidate what I am saying

I just had a game where I was 3/8 - my KDA wasn't even that bad, given I had 15 assists, but the Tristana on my team only paid attention to the 3 kills and 8 deaths I had as Malzahar - I said her to buy a because the enemy team had so much armor and she would need this item to deal significantly more damage to them. However she started to insult me and say that I was wrong because I was 3/8 and she was 13/14 (to be honest, 13/14 is actually a worse KDA because everytime you kill someone, you reset your gold value - I died so many times with so few kills that I wasn't worth any gold, but Tristana was actually worth a lot of gold for the enemy team) We still won because we managed to focus their carries and push.

However, I don't understand why people use KDA as an argument, since it has literally nothing to do with what I say - I may have 14 kills and 3 deaths and still be giving the wrong advices, and I may have 2 kills and 9 deaths but I am still giving the correct advices, but people won't listen me because I don't have 14 kills and 3 deaths, but 2 kills and 9 deaths.

By the way, on the same game above, Tristana was also insulting me calling me a "gold scrub" (even though I am actually a Diamond V player) - I don't understand what my elo actually has to do with me saying to Tristana that she needs to buy armor penetration items. Every high ranked player knows that unless there is only one or no champions stacking armor, it may be better to buy armor penetration, to ensure that you deal the most damage possible to enemies. On the afoermentioned game, there were THREE enemy champions stacking armor: Lee Sin, Nasus, and Morgana.

I even avoided saying my elo because I knew that not only Tristana would not believe me, even if she indeed believed me, she would not listen me regardless, or she would probably say that I was boosted (yet another fallacy; just because I played poorly in one game, despite being high elo, does not mean I am boosted)

Link to the aforementioned game: http://matchhistory.br.leagueoflegends.com/pt/#match-details/BR1/910578803/201721804

---

I would like to understand why people use those two fallacies, the KDA fallacy and the rank/elo fallacy. There are better arguments you can use when you don't want to listen to someone's advice, but using their KDA or their elo is just an insult. It is like saying that what I am saying is wrong because I am not rich, I am poor.