@Riot Is Not Playing the Objective of the Game a Bannable Offence?

If a player queues up and joins and then intentionally disregards the goal of the game, which in the case of Summoner's Rift, for example, is to take down the nexus and win the game, is this a reportable offence? And will Riot take action against these kinds of players?

As an example, and looking especially at normals: you queue up for a game. As the game is coming along one particular player seems to be playing with no regard to what would actually help us get closer to winning. He is going around taking whatever he wants, doing whatever he feels like doing, knowingly screwing over his own teammates and his own teams chances of winning in the process. When asked about why he was playing this way, he responds with "It's a normal game, I'm messing around, I don't care about playing to win". Is this considered acceptable? Because I have a hard time thinking it should be.

The first problem I have with that kind of mentality is that this person thinks that just because they play ranked it makes them entitled to come into normals and disregard the objective of the game completely. They ignore the fact that not everyone plays ranked and some people prefer normals. But they don't care about ruining the game for these people because in their eyes if it isn't ranked it doesn't matter. Secondly, griefing your teammates and knowingly contributing to your teams loss just because you felt like "messing around", shouldn't this be considered the same as AFKing or "Assisting Enemy Team" in a sense? Because if you're intentionally not trying to help your team win and making it harder for them to do so then you're basically doing one of those. Thirdly, disregarding the objective of the game and not playing with the intentions of winning ruins the quality and spirit of games and goes against the purpose of Riots design. This is targeted towards multiplayer games with PUGs involved, where you are directly hindering other players experiences by not staying true to the goal of the game.

TL;DR Should intentionally not playing to win be reportable and is Riot taking action against this type of behavior?