Because IAMS, being part of the Proctor & Gamble group, are part of such a big conglomerate they can get away with murder (literally in the case of the animals on whom they perform vivisection). They put statements out to the press contradicting the findings of the animals rights groups and - well you only have to read some of the posts on this thread to see how people believe them, rather than the truth the protesters have unearthed.