What a bunch of baloney. Joel Zimmer said it best in stating that "people need to realize cameras don't equal terrorism." If this is the case then one can easily attribute Google, books and films to facilitating clandestine movements since you're likely to extract as much ideas and information from there as well.
By urban exploring, one is merely expressing admiration for a particular environment and subsequently helping to preserve and showcase a place that not many ever get to see or were aware about.
Interesting article that I suggest reading if you also happen to have a sweet spot for urban exploring. I'll admit to dabbling with the hobby from time to time.