The problem is that LoL didn't have this software before and now they do, so for players who may not have experienced problems they might be now.
eSports has grown enormously around the world, with sponsorship and real money on the table. Unfortunately, that has pushed cheating to a whole new level where people will develop and run very sophisticated cheat software. Anti-cheat software therefore needs to see where the anti-cheat software runs and lives, which unfortunately means that anti-cheat software is now running to run at very low levels in the system and has the ability to play havoc if there are bugs.
I genuinely believe that developers aren't developing this software to be nefarious but to provide the best experience for players. Anti-cheat software has been around for a long time and its not the first time its blocked other applications from running.