Do you need to pay to access Steam and play games? The answer is no - there are free games on Steam and also forum features that allow you to post media content too. From that standpoint they're in the same boat. The difference is the platform's intended use.

I think the real issue isn't about Visa and MasterCard trying to gatekeep/censor this. The talk should be about we as a society haven't matured enough to be willing to talk about our own bodies as humans and human nature with our own kids. If you look at what's shown on mainstream TV around the world, off the top of my head, Europe seems to be a lot more mature about it than many parts elsewhere.