Defacing ancient ruins and defecating in public doesn’t help:
Another reason could be that the Chinese lack a guidebook culture:
The Chinese have gained wealth so quickly that they have become thrust into global tourist culture without the time to create guideposts that other nationalities might enjoy. For instance, there is no Chinese equivalent of Lonely Planet, encouraging young Chinese to go explore the world and respect the cultures and communities they enter.
Plus, bureaucratic and language barriers encourage group travel:
In many countries, Chinese are still viewed with suspicion during visa review processes. Chinese tourists always seem to travel in huge packs because joining a tour group makes getting a visa easier. Finally, tourism sites across the world have learned to accommodate the language needs of the English speaking world, but Chinese tourists are rarely fluent in English or the language of the country they’re visiting, leaving many opportunities for miscommunication and misunderstanding.
Another reason why Chinese tourists are so unpopular:
[O]ne thing many Chinese vacationers don’t want to do with their money is tip – a custom in some places which many have ignored, Wang said. Though most travel agents in China would educate their clients about tipping in a foreign country ahead of their trip, most people ended up tipping very little or none. Some are not used to the idea of tipping, and they fail to understand that staff working at the Maldives resorts, who usually earn a meagre salary, rely heavily on tips, Wang said. This has created increasing tensions between the Chinese and their hosts. Staff would naturally prefer serving guests from countries with a tipping culture. Other staff have gone after Chinese clients and asked openly for tips, a rare thing for them to do in the past.
Of course, having access to guidebooks is no guarantee of good manners; Americans are still widely viewed as the world’s most obnoxious tourists.