One theme that McGrath refers to frequently on his blog is the responsibility believers have to follow evidence and use their mind. He says it well in his newest book, The Burial of Jesus:

Faith may go beyond the available evidence, but if it contradicts it, it is at best wishful thinking and at worst a delusion or a lie.

One of the big problems with modern Christianity is that our faith has gone beyond the available evidence, without option for reevaluation once new evidence is found.