Pants are Dragon, a challenger level YouTuber/streamer, has had gold players in a couple of his challenger level games, and he's above rank 50 in NA and has goog MMR. There's a good explanation, though: the longer you're in queue, the wider the MMR gap it allows. If you're in queue for a long time, you can, even as a challenger player above rank 50 in your region, and especially at the beginning of the season, when MMR is still fucked up, you can find relatively low ELO players. Now, should this diamond have reacted like that? No! Allowing himself to tilt only made him play worse and his raging likely tilted at least one of your teammates and made them play worse. If anything, his raging instead of taking charge and telling you what to do lost you the game more than anything else. Thought that people were supposed to learn that the more you use the keyboard, the less likely you are to win in the process of getting through plat. At least, that's what every diamond+ YouTuber I watch has said. What I would do if I saw that guy is ask him to shotcall instead of complaining because he's a diamond playing with golds and that should be a huge advantage. I've carried a game as Kha mid where literally my whole team was feeding (except me, I was fed), and they were trying to surrender at 20 (the enemy team had a 15,000 gold lead) just by shotcalling. That game lasted 75 minutes and remains my longest game to date, but we won with a 6k gold lead. If this diamond player had done the same thing instead of raging at you guys, you probably would've won.