

It’s much worse than that. How they word it is “if it may damage the public image of mastercard”. And they don’t review the content, they review the means used to prevent the damage to their brand.
So valve doesn’t even need to have anything that actually damage mastercard brand, it just need to be that mastercard is not comfortable enough with the measures used to prevent it.
What I read is that it is not about illegal content. It is about the measures taken to prevent illegal content from being sold. It’s much more devious than simple censorship.