Why did Theroux say that the Malay smile was misleading?

Despite the nation's prosperity (due to the high prices of natural resources), Malaysia was prone to ethnic violence. Theroux had thought the nation peaceful and the people non-aggressive when he first visited in 1969. However, shortly after making this assumption about Malays, rioting Muslims slaughtered 2,000 ethnic Chinese and burned down hundreds of Chinese-owned shops. Theroux said the Chinese lived in a state of fear in Malaysia, keeping a low profile to avoid attention.