I would have a lot more respect for poptimism in general if they could use descriptive language to explain why they like that music.
Fans of any other genre can usually point to the dynamics of a song, a certain melody or rhythm, or the performance of a certain instrument or musical part that they consider to be "good" or at least "interesting."
Poptimists, at least in my experience with them on /mu/, never go beyond saying it's "just fun," or it's "just corny and stupid, whatever," or "it's not meant to be taken seriously." That last one I consider to be the worst offender, because that seriously erodes the quality of any artistic discussion in general.
If they could talk about why they appreciate their music like adults, I would respect them. Although I might say the reason they don't is because there isn't much to talk about with that kind of music.