Why would you say anything to bad teammates? You wanna rub it in their face that theyre getting outplayed?
Blaming players is against the rules, so if they blame you, tell them theyre wrong, and report them.
No you cant talk trash as a duo, a solo, a trio, or a 4 man.
Okay.
As far as how to deal with them, just accept that other people's skill is out of your control. Maybe their lane opponent is slightly better. It actually doesnt matter why theyre doing poorly. Either way, its not something you can do anything about. So focusing on it only hurts yourself. Literally. Getting mad about it will seriously only hurt you more. Theres no benefit to it. I know you cant help it in the moment, but take a breath and recognize that its a video game and this is just how life is. You will lose half your games. Accept it.