Obvious question but wtf is wrong with Harry

I'm on the 4th episode of the second season and in the flashback why on Earth does Harry tell Dexter to lie to the psychiatrist, like what possible harm could come from Dexter being diagnosed with whatever mental problem he has. Say the psychiatrist finds out Dexter has homocidal urges, then worst case scenario he's taken to a facility and given the help he needs, it doesn't make him any less family, I can not understand what issue Harry could possibly have with this outcome. Starting out, I could kind of see Harry choosing to tackle Dexter's mental state himself as a sort of misguided "Man of the House must take care of everything" deal, but this goes straight into sabatoge of Dexter's future for no reason I can think of. Sorry, just venting.