Indeed. I suppose that there is a blackmail risk: their stake could be made worthless unless Naspers has Prosus have the Stack Exchange people ban Tor, but I rather doubt this happened.
How could Tencent selectively make the shares that Naspers owns worthless?
One could consider what's now happening with Alibaba ADRs and the fear of delisting. The price on a certain exchange crumbles. However, I do wonder if at the scale of a big company owning big chunks it'd just be a minor cost of doing business to reregister for the HK exchange?
Something tells me a shareholder suit by a foreign company in Chinese court, in connection with not blocking internet traffic, would not go down well for Naspers :D
The proper word would be extortion - the Chinese government could in theory make demands of Naspers by threatening to hobble Tencent. It's pretty far-fetched, especially since Naspers owns a minority (28.9%) stake in Tencent.
I mean, Tencent could just be forced by new Chinese law to buy back Naspers stock for $0.001/share. What's Naspers going to do, sue in a Chinese court? Go to war?