Honestly, regardless of what division or elo you're in, flamers/toxic players will always exist. There's not much you can do about those kinds of players so it's best to just play your best and report them afterwards.
What it seems like you're running into is players who are having a bad day, and just need some encouragement to get back on their feet. Or if they made some mistakes or gave up first blood, they might need some help catching up. When someone is stuck in a rut or can't seem to bounce back, I usually try to be encouraging or positive. I try to give them a "awesome!" or "gj!" whenever they do something great, or give them a "No worries" or "No sweat. We're good :)" if they make a mistake. Players can get stressed out when they're doing poorly, which happens at every elo no matter the skill, and might cause them to get agitated or not want to cooperate to help win. I usually main jungle and support, so anytime I see someone struggling I always try to encourage them and help them with extra ganks or letting them farm more.
Positive reinforcement and feedback always seems to help whenever that happens to me or my teammates, so I might suggest trying that method. Be very careful how you word things though! Intentions/emotions over text can get easily misinterpreted, so don't type things that might not get across easily.
Just think about what would help you bounce back in a game if you were struggling or falling behind. Some people usually focus harder, others need encouragement, and some just need a little push with some help from their teammates.
Either way, the toxic players will exist, and no matter how you act they'll never change. But it's the neutral/positive players you always want to help and continue helping. Because there's a very good chance they'll help you back and help you win :)
(It sounds extremely corny/sappy but I do mean when I say that you'll win a lot more games with you and your teammates play with positive/helpful attitudes. It all comes down to being supportive and friendly. Haven't you ever seen the Did You Know? fact before each game that says positive players have a higher winrate than negative players? :P )
