I beg to differ. I don't speak or write mandarin but I speak Hokkien and Teochew. "Most" chinese don't include people like me. I get annoyed whenever people meet me and tried to speak mandarin with me.I think the truth is most Chinese in Malaysia have adopted Mandarin as their mother tongue beside the dialects, some even can't speak dialects.
The main reason for the opposition towards the use of English in Chinese schools for the teaching of science and mathematics is that the Chinese educationists fear that it will make Chinese education and Chinese vernacular schools irrelevant. Even the closure of Chinese schools is a sensitive issue because it will limit opportunities for Chinese education in the country. That is why Chinese educationists are fighting tooth and nail against its implementation. They do not care about the benefits of English. Somehow, the Chinese can adapt as I have cousins who had studied in Chung Ling High School in Penang and had become successful engineers after having studied in Australia. Some elements of English teaching was implemented quite successfully in Chung Ling High School then and should be followed.