CHENSHENG LU hardly cuts the profile of a provocateur. He dresses business casual and wears silver-rimmed glasses. He lives in Wellesley. He gardens. He has two children, one in high school, another in college. He occupies a tidy office in the Landmark Center, as an associate professor in the Harvard School of Public Health’s Department of Environmental Health. And yet the mention of Lu’s name in certain quarters elicits palpable discomfort: Oh, him.