The rift has nothing to do with the political system (e.g. the US is freely and openly allied with Saudi Arabia despite radically different political systems), and everything to do with the competition for power and influence in the world. SA is not a real contender there, China is. From here the rift and inevitable conflict.
> If you are looking for some specific justification for a ban, you're missing the forest for the trees
Every reason for the ban comes from the above competition for power and influence in the world. Whether it's not having an adversary financially profit from your own citizens or influence their decisions, or it's to eliminate foreign competition and fill the gap with local companies, it's all abut power and money and the political system couldn't matter less.