Further to my last post, there is another far more prosaic reason that research using Primates (monkeys) is very much 'above board' and that is there is a huge shortage of monkeys for research. They have to be specially bred to be totally free of any hint of disease , and demand massively outstrips supply. No research institute that had the most minor question mark against its animal welfare policy would just not get supplied with animals, here is a link from a few years back,
http://www.nytimes.com/2004/04/06/science/monkeys-for-research-much-coveted-and-hard-to-come-by.html?_r=0
the situation is FAR more acute now and the price of a primate for research is now up to £50,000 each!! They just can't afford to waste such a valuable asset by using them in a less than ethical manner.