I can't tell if Maruyama is indulging a bit in being a (honest) douche, but I feel like a big part of why he did this is him being nice. Even if he is one of the meaner cast members and Mamoru (probably jokingly) said that he might have good points a few chapters ago, I feel like Maruyama can't be a truly mean person.
(Unless it comes to couples, good looking guys, and other categories he might be jealous of, but this is this and that is that.)