I feel like this should be pretty obvious, but please don't talk shit about your bot frags or people who are having a bad game- it's not going to make them play any better unless they play better when they're mad at their team (unlikely), and it just ends up bringing down team morale.

Case in point: Me, on Reyna, going 5-9, with my 3/4 of the rest of my team shidding on me, saying that I'm an embarrassment, I need to uninstall, fix my shit, and so on. 1 person (thank you kind stranger!) stood up for me a little bit and just that one act of someone being nice to the bot frag boosted my confidence infinitely. I ended up Team MVP by the end of the match (even though we lost 11-13).

tl;dr: try to be nice to the bot frag. Lift their spirits, and they'll probably play better as a result.