Found YouTube history that made me sick

Started checking my 8 year old's YouTube history after a teacher mentioned some behavioral stuff and found he's been watching videos that are way too old for him. Stuff that's technically not blocked but is clearly designed for older kids and has some messed up content. Had to have a talk with him about it. Now I'm paranoid about what else is out there. Do any of you actually monitor this stuff or am I being crazy?