This is the exact opposite of consent. People are being forced to install the anti-cheat software. While you may personally find it acceptable, you do not have the authority to consent on behalf of all other players, therefore it is not consent but simply an opinion.
Installing the anti-cheat software on your own computer will provide you absolutely no benefits. It needs to be installed on the cheaters' computers for it to be effective. Obviously if there was actual consent involved and people were allowed to not install the anti-cheat software, then cheaters would simply not install it.
There are plenty of valid reasons to be concerned about this, even for people who have no intention of cheating at all. While you may trust Riot, others may not. Even if Riot won't do anything nefarious with it, all software has bugs. It's only a matter of time until someone finds a vulnerability in Riot's anti-cheat software and actual malicious actors start to exploit it.
I hate cheaters as much as anyone else, but an anti-cheat program running with kernel-level privileges is simply a ticking time bomb and should never have been approved by Microsoft. But of course, it's easy for gaming companies to brainwash the masses who have no awareness of security and privacy risks with "you don't want cheaters in your games, do you?" These are the same people who get brainwashed by arguments like "if you're not doing anything illegal you have nothing to hide, therefore you should have no issue with your communications being surveilled 24/7 because it will help reduce terrorism".