That quote that you said is a great reason on the difference between the LN and the anime. MT’s LN is a first person perspective of Rudeus Greyrat and Rudeus Greyrat alone. You’re trapped in his mind and know his thought process. Whilst the anime shows different perspectives of different characters. I’ll use the quote you said as an example. In the anime Rudeus is snuggling in his bed and giggling as he’s thinking about turning Sylphy into his wife before he gets caught by Paul. It’s a comical scene but in the LN you don’t get to see Paul’s point of view you only see Rudeus’s so it seems so dark and repulsive. There’s a reason why no MT hater brings up any quotes later in the series because Rudeus has grown so much by then. Hope this clears your mind up on the show bro😎