Person with a Twitch account thinks harassing their own team is better than playing

Not saying Twitch is the main reason for this nor that all Twitch users who play league are like this.

I played a ranked placement game (game 8 out of 10) and got stuck with someone who has "TTV" in their summoner name. Okay they stream, they must be streaming. Throughout the game, this individual decides to harass our team:

Bot lane was doing well but knew this person was not playing seriously in a ranked game. Mid was struggling to get somewhere while this person called them "Silver trash" I was stuck top against a playing as asking for help a lot since they had a lot of jg presence topside.

This person played jungle Olaf, a champion that does well in 1v1s or can change a 2v1 around given the enemy is low hp. Instead for example throwing his Q to finish the enemy jungle off, they smite them at 11 minutes into the game, throwing their smite on a 50 something second cooldown. They did this with almost all of the kills they got, which left objectives to be easily taken by the enemy Nunu. I called them out on that by saying they could save smite and use Q, but they went on with "IMA BOSS". They also claimed they were a "grandmaster" player when our support called them "Silver". As the game progressed, things got worse since our bot lane who were doing well is now doing bad. The Nunu got ahead, shortly after their team got ahead and was securing objectives. They got the dragon soul and all but 1 drag while our jungle went top to take 1 wave, roam mid to take a wave or two, roamed back to top, and repeated. As soon as the game ended, they exploded in chat with the usual "report this team, trash silvers" and I quoted the grandmaster quote. I left the lobby to find a friend request from them in my inbox. Shouldn't have accepted knowing they went "hope you get banned, you'll see why." I checked to see if they were streaming, they were, the entire game.

When I say this isn't against all Twitch users who play league, but every time I have played with someone who has a twitch, they're 90% of the time toxic towards their own team. Is this what brings views in along with money or is this a bad representation of what Twtich users should be? I don't use twitch nor really watch livestreams (last time I used it on my computer I got a virus so I haven't used it since) but is there a way to report this person for streaming their toxicity or if that's even a thing on twitch?