Terry Fawles is clearly mentally ill, so you can chalk it somewhat up to that. (spoilers for the rest of the game) Dahlia is also a serial manipulator, so it wouldn't surprise me if she went out of her way to manipulate someone she knew was mentally ill and much older than her so that it would be easier for him to take the fall. This does fall into the trap of blaming Dahlia for being in a relationship with a 20 year-old man, and fails to examine if that relationship influenced her to take the actions that she did, but either way, T&T as a whole does not act like this is a good and desireable thing, and neither do any of the characters that aren't Terry or Dahlia.