In my research I have seen a lot of back and forth among jihadists even within AQ about who is holy and who is an infidel. Seems these guys are so pious that anybody who doesn't follow their dogma is an infidel. I took that sentence as more of the same, but there are many possible meanings.
Yes, it's possible he simply means because we're infidels we're the terrorists, since he considers himself too pious to be anything but morally right. Then again, I've heard before over the years Arabs claiming the US was behind terrorism and framing them for it...so yes, there are many possible explanations.