The conference http://gesalerico.ft.uam.es/strings07/040_scientific07_contents/041_speakers.htm is about string theory, not other approaches to quantum gravity. It should be quite clear to anyone who understands LQG-like approaches to quantum gravity that there is not one single word in Witten's presentation that has anything whatsoever to do with LQG-like approaches to quantum gravity. What he is doing is returning to a subject for which he's made a number of important contributions to in the past which is (2+1) dimensional gravity. As he says, his motivation for doing so is to obtain a quantum theory of BTZ black holes which he believes is possible for negative cosomological constant since it is only for these values of the cosmological constant that black hole solutions exist in (2+1) dimensional gravity. He invokes a number of ideas, all of which are related to string theory and none of which are related to LQG. Most prominent are conformal field theory and the AdS/CFT correspondence. He also brings up the subject of gauge theory descriptions of (2+1) dimensional gravity, but only to demonstrate the serious problems associated with these sorts of gauge theory descriptions in this context. On the other hand, people in lqg continue their search for legitimacy by trying to find ways to connect their ideas to string theory.