Do you still expect to win after flaming/being toxic?

I mean that's why you (generalization) start behaving out of character, right?

I don't get it,

What is the motivation beyond any selfish intrinsic reasoning?

What is there to gain by bringing negativity to someone else's life for 20 minutes?

After realizing its not constructive, why do you not expect punishment?

Riot is explicit about player behavior: You break a rule, you face a consequence. no one should be rewarded for being crappy to someone else.

i main mid, I've lost countless games with a 1+X:1 ratio. I have never BM'd losing lanes, because I always thought it to be pointless.

Using derogatory language, even calling players bad, doesn't make them want to play better. There is nothing to learn from that.

I've seen only tilts and RQ's from bming. I wouldn't want to play a 4v5, 0/3 adc or not. some nice words and play strategy can change that adc's outlook and approach. (unless he is BMing himself.)