Perhaps he doesn't forget, but wants to speak about what you should do today. Or, perhaps he doesn't know about Java 8 lambdas. Ultimately, your comment would come off a lot less offensively if you had said something like "Interesting article. I wonder if Java 8 lambdas will change this. <link>".
The article has a point. Guava is pretty nice, but using anonymous inner classes to implement filters gets pretty ugly.