I don't think it's as easy as who is anti who. Both US and Taiwan (and China too I'm sure) are trying to make the best out of the situation. Plus, if you study the political environment in Taiwan, you'll know that the opinion among the whole population is not unanimous. You are correct that Taiwan is not totally anti-China, and the reason is that there is really no good reason to be at this moment (except maybe if you want to use it as a political slogan to run for an election)
Also, investing in China is not a decision from the governement.. it is strickly decision from the people that do business. There was a news a while ago about the biggest company in Taiwan (or used to be... the Taiwan Plastic CO.) was planning to invest major money in CHina, but was delayed by the government because the amount is too big. What I'm trying to say is that there will always be business exchange, but the political issues are still sticky issues