I don't understand....

so I'm a bronzie right. I was playing a ranked game with my friend and we get a smurf who says hes in diamond. So i was complaining to my adc who's my friend but I'm not for real and my friend knows I'm not serious and the diamond lee sin decides to talk, so we are in a argument about how I'm toxic and how he's toxic. I bring up how everyone in the game but my teammates thinks I'm toxic but I'm running around as support helping everyone even the lee sin but lee sin legit doesn't even help one of his teammates. He goes I kid you not "I don't have to help I'm in diamond and I don't care if you lose this game at all" huh......... I just don't get it why do a diamond player come into a bronze game and says he don't care if we lose this game at all. This guy name was alexlaw8 this is his smurf and I looked at his account for this smurf. I mean he gets a lot of kills cause he's facing bronzies but that's cool an all but then hes just plays rank and either don't help and ruin the game or gets so fed to the point they just ff. Man I'm kind of starting to hate this game a lot, this dude really made think about why I should even keep trying to play and get better. IT'S NOT FUN FACING A DIAMOND....