At this point in history, you're right, China seems to be a very unattractive target for terrorists of any kind. I think that can be attributed to a number of reasons. For one, the security services in China are very capable and strong, and they aren't constrained by legal rules. Also, the Chinese government seems to have the support of most of its population, fairly homogenously throughout the country. Even in "danger" areas like Tibet and Xinjiang, the percentage of the population that might aid terrorists is quite small. Foreigners and certain minorities like Uyghurs can stick out like a sore thumb in China, making operations in most areas of the country that much harder. It's also (if I understand correctly) pretty hard to get your hands on weapons and explosives in China.
But it hasn't always been this way; in the early 1900s, leading up to the overthrow of the Qing, lots of revolutionary groups conducted fairly classic terrorist-style bombings and assassinations of Qing officials regularly. And I would imagine that similar activity continued throughout the early part of the 20th century, although so much history from that era has been lost (at least to the English language) that it's hard to say.
I also do agree, that even amongst the minorities, most are more in support of the government than those rebel groups. One of the primary reasons, that I think we have to look at, is public content levels with the government. When public disapproval and anger is much higher than the support rate, it doesn't take terrorism to start trouble; rather the people will revolt and start uprisings on their own. Pretty much every dynasty ended that way. If all is good, rebels and resistance either won't last as long, or aren't as big, and won't garner as much sympathy as they needed to get their movements through. And it all depends whether the government is doing its job good enough to keep the content levels higher than the discontent. Example includes how Ming resistance post 1644 also did fail eventually, how despite initial dislike of the Qing government, it survived further on. In contrast, Taiping and Boxer were a start of more major rebellions which actually made it into history, and the same time, they also marked the time when Qing is in trouble. Pushing the box a little by little, timing came ripe with Sun's organized uprisings, along with the weakness of the Qing at the time, which actually finally made it through.
These are all my personal opinions of course, but I see a similar trend that can describe the Chinese then and today. Chinese wanted stability and "mind their own business and bring food to the table" more than anything, throughout their history. With that said, most also knew the instability that revolts bring, and the chinese generally don't agree with "terrorism" tactics, so it's not very popular..unless 1.they are sympathetic to the rebel's cause 2. the cause is important enough 3. the cause affects them (such as tyranny) 4. they deemed the cause to be right... which then they are more likely to support it. With that said, this is why the ability to provide stability and content to the people is truly the government's priority in china, and it is effective. the same can be applied here. most of the minorities are either content(or appears to), and they benefit from affirmative action and the stability. on the other hand, han makes up for the majority of the the chinese demographics, so naturally so's the support and the dislike towards terrorism. with even few support within their own ethnic groups, not to mention their fear tactics and methodologies traditionally is greatly shunned within the mainstream culture, and that their movements will harm the very people they are fighting for, this makes their movements even more unpopular.
the term "freedom fighters" almost doesn't exist in chinese culture; only "revolutionaries', or "rebels" and contemporary, "terrorists". unless you can prove to others you are a revolutionary, you're just a rebel, and no one likes rebels. it sounds degrading enough as it is. for these groups, they wont even get a recognition for anythign more than the term "terrorist"
furthermore, groups like al qaida gave them a bad rep, making it harder for them. another thing is that these groups are very small, and aren't strong, organized, or networked as other international terrorist military organizations out there like al qaida.
if the ccp gets serious and slams a real iron fist to the western regions on these groups at the same magnitude of a cultural revolution, it's no doubt these groups will be rooted out for good.
Besides what you described would be more seen in post 9/11 US than china.