Honestly there's a big difference between RL and OSB. This is due to the nature of open source and anyone allowing to edit it as they please unlike with OSB. This makes it hard to curate which plugins are being used and/or are allowed. Even back then there were a lot of controversial non-official RL plugins floating around and they were very detrimental to the game integrity and very hard/impossible to detect. This scene has only grown, and now we have even crazier plugins going around that can do very questionable things such as one-way-safespot highlighting/overlays, PVM plugins for new content (hydra, vork, zulrah, cox, tob and even some inferno ones).
I was in the same boat and didn't understand at first why RL was being targeted over OSB when they seemingly did the same thing. But I'm more inclined to side with Jagex nowadays after learning all of this. I feel if they improved the official client or bought over OSB and then banned all 3rd party clients, this would be a non-issue and the right way to do it. It's not a simple issue and it doesn't have an easy or cheap fix, so it's hard to judge them based on this. I feel like they should have communicated better with the community back then, and now it feels hard to go against the wishes of the community.
I only have respect for Mat and I believe he has always wanted what was best for the game.