As I like to form an opinion from looking at both sides of the coin below is an article showing the CME's response to their reason for the margin hikes in detail. They have a strong argument as to why the hikes are put in place but i'm no expert in this field.
http://www.zerohedge.com/article/other-side-story-cme-understanding-margin-hikes-and-why-they-are-not-means-move-market