Let’s get a couple ideas out of the way. (1) Most, perhaps close to all, people who are religious see terrorism as abhorrent and feel killing innocent people a violation of their religious principles. These people work hard to build community. (2) There are terrorists who are not religious.
Even so, those who engage in terrorism for religious reasons can be especially dangerous.
Religious faith really does motivate people to do terrible things. If you really, really believe that your god wants you to be a martyr and to blow people up, then you will do it. And you will think you're doing it for righteous reasons. You will think you are a good person.
Dawkins refutes the claim that only religious people selflessly take care of others. Yes, there currently is a great deal of infrastructure and money in place to make it easy for religious people to show their care. But atheists are beginning to build their own infrastructure and raise money. This includes groups such as Secular Rescue and his own Richard Dawkins Foundation.