Getting toxic in response only makes the match even worse for everyone in it. "Fighting" them by doing this doesn't improve a toxic situation nor help get them punished for behavior, the only way to do this is to ignore/Mute them and report their behavior at the end of the match.
We all feel the urge to respond to these people and "give them a taste of their own medicine", but it's not very constructive or mature. A little bit of negativity is normal, and Riot won't punish you for getting upset, but if you're going overboard and using extremely offensive language or being a problem regularly in your matches, that is when you start getting penalized.
Muting players that are being jerks in chat is the best defense, and it doesn't reduce the effect of your reports against them (even if you can't see what they say, the system will still check that if reported, and every report always results in a review). If you are feeling tilted after a bad match, I recommend backing off and taking a break from the game to cool down, or at least play a less stressful mode like ARAM or do a little practicing in vs. AI.