If it's an open post, there's nothing stopping you. I'm also not arguing that point. Because I know what you're referencing. However, I've never seen any comment from any Riot support member indicate that most chat restrictions have been issued to players defending themselves. I've actually seen exactly no statistics on that at all.
That is why the tribunal worked and this system punishes ppl defending themselves from major abuse
Notably, the Tribunal clearly instructed players that retaliation was not considered acceptable, and to focus on the player they were judging, not what others said. Riot may be stricter about enforcing that, but it's always been a thing.
And they've always said they'd be stricter than the Tribunal was, so it's not exactly a surprise.