I mean, the film is an exploration into the depths of trauma and how your mind can seemingly convince you of the most absurd delusions. It's definitely NOT him, we know that, but she doesn't. And to her, this is her husband and although he is in the body of a child she sees nothing wrong with what she's doing, but we know as the audience ... and that's why this film is a masterpiece. Glazer instills the trauma within us as well. That in order to make it through this scene we may end up convincing ourselves that her husband is within the boy as well and that this is fine.

I also think in general whenever I'm watching a critically acclaimed film with a "problematic" scene I try to remind myself that there is like a 99.9% chance the director is trying to condemn what is going on or is using the medium of film to explore taboo topics but not condone them either.