Because a) it was reported as a suspicious source and b) upon examination was found to be “Mixed for factual reporting due to poor sourcing”.

https://mediabiasfactcheck.com/south-china-morning-post/

That is not an issue other sites that we do allow have. The decision has been made. It’s not up for debate.

When the links were removed, the user was not banned and simply told to choose better sources. They went on a rampage reporting posts from known reliable sources resulting in a 3 day ban from a separate mod for abusing the report feature.

All of this was explained to the banned user who kept arguing and arguing in PMs and was told to stop, which resulted in increasing their bans over and over as they persisted until they were finally permanently banned.

In the end, their behavior in PMs showed the banning was appropriate. You don’t get anywhere arguing with mods.