They have the right to play poorly. You don't have the right to flame your teammates. Chewing out your teammates only makes them play worse, not better. There's no benefit to flaming.
If they're intentionally feeding, then by all means, report them, and let Riot deal with them. If they're breaking the rules, they'll get actioned, just like you would for flaming.
If you want to play with people of around the same skill level as you with incentives to play your best, play ranked. That's what it's there for.