What is the limit to tolerable and abusive teammates?

I've recently played several games with some really toxic individuals. personally I've learnt to keep my mouth shut for the most part and aside from getting into a rare back and forth joke/conversation with a teammate or opponent or to ask something of a teammate, i.e buy control wards, correct item path etc. I used to be somewhat toxic, if you consider responding to toxicity by defending the one getting abused toxic, but after two penalties I've learnt that getting into an argument with someone in game ends up bad for me. Now recently my teammate went so far as to tell my other teammate that they hope his parents die of eye cancer, all because he couldn't a lead of kills he stole from us was lost (repeated tower dives). I've lost family to cancer and one of my friends is currently dealing with the disease right now and this remark really bothered me. I'm usually more uncaring but for this guy to say that out of nowhere like that...it just bothered me, I asked him why on earth he would say that and his response was "get off your high horse" to which i responded with "there is no high horse, cancer is not something to be thrown around so lightly". He actually typed, "I hope your parents murder each other in a fit of rage". This is just the latest in a spree of toxic players that have come across in the last few weeks and I've reported every one of them and yet they are still playing, some of them have gone so far as to add me just to taunt and then unfriend. Is this actually acceptable? I thought surely that with players being banned for asking to report toxic players, the actually toxic players would get some penalties as well? is the only option left to just mute and ignore? Because we certainly can't engage them, can't talk about reporting them and leaving a game where a player's sole objective becomes to ruin your game gets you penalised. Is there really nothing that can be done? Now for sure I am no saint but i am not toxic enough to wish cancer or death on a teammate's family because of how I'm doing in a game, but this is really rubbing off on me, I'm becoming much harder to be around, might quit the game.