Point number two is the one I disagree with more. There are lots of people that cannot exercise vigorously on a consistent basis. Walking can absolutely provide a benefit in bridging the gap between workouts. I find that walking is most beneficial to people that are confined to more sedentary lifestyles, sitting 8+ hours a day at work will take years off of your life. There are people with various injuries and maladies that prevent strenuous or exercises involving high-impact. For them, walking is one of the few things to keep them moving and prevent atrophy. Absolutely vigorous exercise is the best option, but to say walking is a "complete waste of time," is a bit short-sighted.
I have been a personal trainer for the last 9 years, and a martial artists for 26 years. Just my 2 cents