Unless you were throwing around racial slurs and threats of physical violence, it takes way more than 1 game of "defending yourself" to get permabanned. You are given escalating punishment each time;
- 10 game chat restriction
- 25 game chat restriction
- 14 day account ban
- Permanent account ban
Most likely you ignored report warnings and several prior punishments. You are expected to learn from your mistakes and reform, and if you don't, you aren't wanted in this community.
THE OTHER PLAYER IN THE GAME I WAS REPORTED FOR WAS WAY MORE TOXIC THAN ME. HOW COME I WAS PUNISHED?
Simply speaking, retaliation is not an acceptable or justifiable behavior. An argument between two players can easily create a negative experience for the rest players in the game with you. Regardless of the other player’s actions, this does not justify your own behavior. You alone are responsible for your actions within the game. If you encounter a toxic player like this, the best option is to simply report their behavior and move on.
Just mute toxic players and report them. You don't have to deal with them all game, and getting toxic back will only make it worse. "Two wrongs don't make a right", as the saying goes. "He started it" is a child's excuse as well, and is unbecoming of a mature individual.