I cant bother to lvl an account a 3rd time just to get banned for responding to toxic players
That's the key, don't respond to them. They will be held responsible for their own behavior by the same system that's punishing you, but if you don't validate their reports by getting toxic back then their reports won't hurt you.
A permaban is not the result of a single match and a single report, but a history of negative behavior and many reports through several punishments (though extreme behavior may result in skipping punishment tiers). The tiers of punishment are;
- 10 game chat restriction
- 25 game chat restriction
- 14 day account ban
- Permanent account ban
Once you get a report warning or a punishment you should review your behavior and fix it, or even ask here what you can do to improve it so you don't get punished again. If you don't try to figure out what you're doing wrong until you have two permabanned accounts, it's a little bit late; if you're unwilling to change, however, Riot doesn't actually want your business because you're driving away the community.
Certainly anyone can change, though. If you are ever interested in coming back with a reformed attitude, I suggest reading the following articles on sportsmanlike behavior;
The Summoner's Code
Behavior Worthy of a Champion
If you like, we could even critique your reform card and point out where you were going wrong, and how you could've approached the situation in a more positive manner. Even if you don't care about the people you are speaking to it's clear you care somewhat about the account you've put time and maybe money into, so think about your own account if you have to to hold your tongue.