According to the editor of this clip, the original version of this speech probably originated about 1965. Snopes traces it to a newspaper column in 1964. In any case, the present version of it is probably (according to both the editor of this clip and Snopes) from about 1996.
Harvey's little speech is often credited with representing an amazingly prescient prediction. Rather, what it represents, in my opinion, is the discernment that nearly anyone would have with some degree of spiritual sensitivity to the cultural drift of the times.
It's amusing to hear expressions used that are no longer part of common parlance today, like "square," "dirty movies," and "swinging." But his points are direct and hard-hitting.
A more interesting question, perhaps, is why so many would likely find this kind of account unconvincing or downright offensive. Paradigm shift. Greased skids for hell.