I don't think the lecture was worthless, by any stretch of the imagination. However, there is a tricky feature to this, which is that it is easy to see the "motivated" aspects of our opponents' arguments and have a hard time seeing them our own side. I didn't like the way he took the entire field of Christian apologetics, and says that it was an example of motivated reasoning. I sketched out in "On being an apologist" how apologetics might be done without what is being called motivated reasoning.
I thought his lecture got close to Bulverism on a couple of occasions.
My rule is to constantly check my own thoughts for motives, but not try to speak with any authority about the motives of others. However, if opponents think there are no non-rational motives for what they think, and that all the non-rational motives are on my side, I have no trouble pointing out at least possible non-rational motives that they might have. Since they can't read my mind, all the can come up with are possible motivations I might have for believing as I do.