People who talk like that are of the opinion that by Spitting K/D/A numbers back in your face, they can invalidate, discredit, or dismiss anything you have to say. They use it to try and shut down anyone who says something they dont like as if they can use your KDA to immediately claim victory.
you could say "Hey, you know the sky is Blue"
and people respond differently based on KDA
if you are say... 8/2/0 the response is "Yeah I know that"
BUT if you are 0/2/8 the response is "STFU Noob, ur 0/2"
as If them spitting your negative kda back in your face automatically means they win the arguement and your statement is false/rejected...even if it is fact.
1/0 - anything you say is gospel
0/1 - You are a noob, everything out of your mouth is invalidated, and you need to STFU and "git gud"
This is why they do it, this is why I laugh. Because they are so hung up on " I have the most kills, so I am the best, and everyone will agree with anything I have to say ever. OMG look how Awesome I am"
And so anyone who isnt going 28/0 is a noob and says nothing but lies...according to the spoiled call of duty kids who only care about padding thier kda...even if it means the whole team loses. (They could throw the entire match, but will still brag about how great they are, how they "OP Carried this Noob team" because...they have the most polished kda)