How do we know who gets banned?

So today i was in a ranked game, and 1 guy from my team who btw goes by the nickname of "TangadeColores" decided to blame his deaths in all the rest of his team, and so, he started wishing ppl cancer, and that everyone deserved cancer for that game, and that he wouldnt even mind killing some of us himself, now to some ppl ths might hurt, specially the cancer part, cuz ppl dont know but some players might have in their famillies members that had cancer like a mother or a father, so ppl like this r%%%%% dont care about what they say cuz they somehow think they wont be punished, so im here asking, are they punished?what does this guy deserve for saying shit like that to someone who had cancer cases in his family?to me this crap is perma ban, but still i would like to know what rly hapens to ppl who say this, and how can we know if this r%%%%%s are punished or not