In other words: Encourage a little bit of criticism, and you will be able to observe those who join in - even if they don't go too far - and be able to obtain a handy register of people to pay extra close attention to.
Nobody is talking about a revolution, that would be suicide. The intelligentsia are far more concerned with using government to their advantage, which naturally responds very well to money exchanged for favors (like how baidu got rid of Google).
It's poor people that government worries about. Because when poor people rise up, that's bad news for anyone in power who hasn't yet fled the country. And if most poor people don't read English, well then there is not much harm in allowing some printed criticism of the Party, as long as it's in English.
"They know that 99% of their population will not be able to read it". But in my experience in China at summer programs in universities, I found that almost all university students (at least in Beijing & Shanghai) can read English. I suppose they will of course prefer to read Hànzì.