Allow me a moment of your time to explain how trolls operate and the reason behind their behavior.
Trolls enjoy making other people miserable for any reason they can find to inflict suffering upon others. They do it for attention, specifically, negative attention. They do not care about you or who your are,. You are nothing more than a target to them and reacting to them only gives them satisfaction on having upset or hurt someone.
Trolls will exploit any excuse to antagonize other people. In league, they may ban an allied pick or steal it altogether. Should anyone announce that they are in their promos, a troll may proceed to soft int to ensure the player does not promote. Throughout a season, trolls find many, many ways to cause others misery. Placements? Ruin players' chances of a good start in the season. Nearing the end of the season? Troll even harder to ensure at least one player does not make their desired rank in the rush. Pre-season? Trolls lock in whatever and excuse themselves with the logic that it's just pre.
Trolling is not exclusive to placements. It's just additional ammunition trolls use against players. And, unfortunately for the people who earnestly try to win with some semblance of honor and dignity, Riot's leniency towards negative behavior is absolutely intolerable. Riot actively refrains from issuing significant punishments until long after an offender has inflicted unnecessary and wholly preventable damage to others.
And while trolls exist at most, if not all, tiers of play, the majority of them reside in lower ranks. These are the smurfs and secondary accounts of players who could not care less if their behavior causes them to lose a worthless account. And players who actually end up permanently banned simply return to the game with an entirely new account and start at the bottom with an entirely unchanged attitude and approach other than the fact they are likely even more toxic, having lost their account as a result of being total fucking assholes.
All you can do to avoid interacting with them is to dodge queues and wait out the timers. Even if you recently dodged, a thirty minute timer is still better for you than having to spend that time suffering their kind. Less obvious trolls who end up in your games, however, are players you ought to mute completely and wait out the match to its conclusion then report and block the player while making a mental note of their username so that if they appear in your lobby again, you know to dodge them.