I think the use of animals for medical research is a very disturbing result of our collective quest for scientific discovery. Although many valuable insights have been found through animal experimentation, it just seems creepy to keep another living thing against it's will to basically torture it, regardless of what the benefits may be.
People sympathize with primates more than "lower" animals, since they are the closest in resemblance to our own species. However, any life form with a nervous system and sensory input is going to experience the same exact sensations that we do when it comes to pain, fear, or discomfort.
I don't know how anyone can not feel bad watching footage of animals in cages or being experimented on. Science should be a top priority in society, but not at the expense of our souls or sense of compassion. There are inevitably sociopaths and sadists in society, but that behavior should be discouraged, not sanctioned.
I saw this article awhile back about lab chimps in the U.S. being sent into retirement at sanctuaries.
It must be a great feeling for the apes to be let free from such confined & miserable circumstances into a natural environment.