Zhang Zisheng has stopped shopping in Hong Kong. The 24-year-old salesman no longer feels welcome, even if his home in Jiangmen is a mere 90-minutes’ ride away on the high-speed rail, and he speaks the same Cantonese as Hong Kong’s residents.“I’m worried that I, as a mainland Chinese visitor, may be physically attacked” in Hong Kong amid the city’s anti-government protests, which have taken on a nativist slant in recent months against visitors coming across the southern Chinese border, Zhang…