"There's no point in telling someone to stop being mean to you. It encourages them and makes you just as guilty."
Hillarious logic! How much did they charge for your brainwashing? They did a great job. Would you like to drown some witches while we're attacking the victims? Asking someone to be nice isn't "just as bad" as a person harassing others and nor is it toxic. It doesn't matter if someone is offended by being asked that or whether the statement is productive. There is objectively no way that such a statement can be construed as toxic by a reasonable person. If you're offended by me saying "Hello and have a great day!" should I be punished for your false report too? Believe me, I have. I actually had confidence in their system then and mentioned it in that chat but it is really just a crude version of mob rule.
Sometimes people may dislike you for all sorts of reasons. Even telling someone absolutely verifiable facts (such as a champion's winrate) may offend them but that doesn't mean such a statement is toxic. Facts don't have emotional content and don't care about your feelings. "Being offended" isn't enough to suggest something is toxic. Your sensibilities aren't my responsibility. When there's no personal attack, profanity, etc. reporting someone is often just a childish and thoughtless response to a contrary opinion or inconvenient fact. It's a lot easier than evaluating oneself. The funny thing is, the most toxic players I've seen are often the first to ask a report on anyone that dares to challenge any of their statements.
Moreover, context actually does matter in the real world and in the philosophy of ethics. It's a critical part of the justice system and also necessary for understanding nearly everything else. This is why we don't judge people from past time periods as being all heartless monsters despite some behavior we now consider abhorrent. Context shapes everything and not having it will never give an accurate evaluation of a situation. Riot currently has no "trial" where you can defend yourself and evaluate the full evidence (not just your own logs) because such a system is unworkable for a company of their size and doesn't provide sufficient benefit either. Accounting for context and giving less/more severe punishment in some circumstances would require a true AI or human evaluation. However, don't confuse Riot's stance with context actually not mattering. It's just way more pragmatic to treat it that way.
If his post is honest and that's all he did, this is just a BS punishment and highlights the flaws within the system. Every report, whether valid or not has some (although not equal) weight and the punishments are mostly automated. Sometimes even quoting a toxic player can flag you by their keywords and get you punished. There are countless flaws with it so don't just mindlessly parrot Riot's line. The only thing that makes the system tolerable is that it is MUCH better than nothing and easier to scale than if you require a human to evaluate such things.