If someone in a movie gets killed, but in a comedic way, (watch 100 ways to die in the west trailer), is it a sin to laugh at that? If someone in a show/movie makes a dirty joke or does something sexually inappropriate, is it a sin to laugh at that? Can a faithful catholic watch south park, family guy, tosh.o and laugh along with them?
I don’t think it is necessarily sinful to laugh at anything. Laughter is generally a knee-jerk reaction, an impulse.
Though, why you would put yourself in the position to watch something that teaches immorality to be a good thing, morally this is irrational.
Use your judgement. Does it teach the immorality to be a good thing? I am more concerned about one anime, Saint Young Men, that portrays Jesus Christ and Buddha as carrying the shrine to a foreign god, than I am about Panty and Stocking with Gaterbelt - even if they refer to God Almighty.
Panty, Stocking, and Garterbelt are scumbags. That’s part of the fun of their misery; they deserve to suffer. Jesus and Buddha are honourable figures (relatively), and to see them bend to the service of a god who is unworthy of their honour is troubling.