For one he has attacked Christianity for being, well, religulous, more than he has attacked Islam. And that doesn't mean Christianity is more religulous than Islam; it means Dawkins is a coward and fears fewer repercussions from attacking Christianity than from attacking Islam.
There is nothing wrong with being afraid to attack Islam. It is a legitimate scary death cult. So is Christianity, but Christianity is somewhat safer to criticize.
http://www.theguardian.com/commentisfree/2013/aug/08/richard...
It's one of those comments that was so obviously stupid and pointless, its difficult to know where to start in responding to it.