Don't forget that a lot of Chinese people are excessively nationalistic to the point where they are a bit insecure. Bugger all will get done about an attack on a foreigner unless they somehow stand to lose face as a result, but when a foreigner attacks a Chinese person even to defend himself, they will usually favour the Chinese guy. Hence, shit TCs will often get protected by default, as people tend to automatically see wrong in the foreign devil. It tends to take a crime against the country itself such as tax avoidance or breaking visa regulations for a TC to register on the authority's radar, it seems.