Grayson is a sociopath who doesn't understands people's emotions and can't grasp situation fully.
You will get it in the next few chapters. Author quckly explains why he went in the basement and thought process beyond that.
He went there not with purpose to harm a boy, Grayson genuinely thinks he helping a kid by spending a time with him in the basement, so kid wouldn't feel lonely while he is "punished" by his father.
And Grayson also thinks a kid should obey to his father punishment, based on how he himself was raised.
Because, again, he can't fully grasp situation, what kid feels and what's wrong with all of that. He judging based on things he learned, but doesn't understands.
Dane will get it as well.
WHAT THE ACTUAL FUCK on that last panel?!
Should I pretend not to saw it or what?!
How come he comes to that conclusion?!
Even if I am Dane, I ain`t loving this whatever creature grayson is
Totally unexpected. Like he is more absurd than the characters in indomitable champion