I've seen quite a lot of toxic people in Overwatch, but I kind of have some fun with them. I like to say "Yesssss, let the hate flow through you!" whenever one of them is acting all salty or blaming others for the team's loss. There's no reason to take that game overly seriously.

If it really gets bad or they start throwing racist words around, I just report and keep quiet. Blizzard actually sends you a thank you message if they take action against someone that you reported, so they do check them out.