The person didn't even mention the reason why they don't like Vanguard and you wrote a whole ass essay m8
It could be due to: having to reboot the pc to turn it off so it doesn't waste resources; the possibility of Vanguard getting exploited since it runs 24/7; having to reformat your drive to uninstall Vanguard; the possibility of crashing their pc at random as many people report or maybe, simply their pc wouldn't be able to handle it.
All of those do not apply to any of the other anticheats nor Google btw
Seconding Kukulkan