People work on information technology always need to communicate and exchange knowledges between countries. If some of them use their skills and technology for blocking people to use internet for certain governments, all the other countries should boycott such behavior.
If they apply to enter U.S., for example to attendant technology conference, as a responsible government has always valued freedom, it reasonable to deny it.
Here is a list of scholars who are working on the GFW in China.
https://gist.github.com/4635732