Many people opposed Nixon's visit to China. Why? I read an article saying people complained that Nixon's visit to China was going against past policies. What policies were they referring to?
Without seeing the article, it is difficult to be certain, but it was probably a reference to the comment that Nixon had made during his trip to Asia in 1964. He said that:
“it would be disastrous to the cause of freedom”
if the United States recognised Red China.
Obviously, by visiting China in 1972, that was precisely what he did.