For people who are assuming it's only affecting gooners and whatnot about porn, I need yall to know that sex happens irl. People have sex, people fall in love, people kill each other, and they keep doing that and more. I've seen a game that I personally know tackles serious questions about depression, suicide, and our place in everything, that game was taken down because it dealt with heavy adult topics.
R18+ isn't just for sex, and even when it is, a card company that acts as the middleman between your bank and YOUR money, shouldn't have control over games or anything else legal you want to buy. Collective Shout got Infamous banned in Australia because one of the characters was abused by her father in her past and it is relevant to her motivations. Their reasoning? "Violence against women". They did the same with GTAV where they claimed you could gun down and torture women on the street and that was the point of the game in their words.
If you've played GTA you know violence can happen but you're not progressing the story by using cheat codes and rampaging through the streets. But CS doesn't care. They lied to get games banned, and they're proud of it! So who else should be able to lie and get creations and art, games, movies, and everything else cutoff from us, not because the content is illegal, but because it's icky to them?