Old Qian has always been a stubborn old soul. He was renowned in the neighborhood as someone who always did things his own way, going about his daily business with his lips tightly shut, not speaking a word to anyone. Qian was a faintly intimidating figure to the children of the alley, who never dared to climb into his courtyard to steal his mulberry leaves. And as the years have gone by, his character hasn't changed a bit; if anything, he's even more obstinate and solitary than ever before.
Jiang thinks this is mainly because his son-in-law had been executed as a counter-revolutionary. Clearly, this has had the effect of forcing Qian to retreat even further into himself, cutting himself off from society to avoid the slightest taint of political subversion. During the mass hysteria of the Cultural Revolution, people were often arrested, tortured, and executed on the most trumped-up charges, including the "crime" that you were related to a known traitor or subversive. So one can understand why Old Qian becomes more ever more obstinate and solitary in response to the terrifying wave of repression sweeping China.