Well, he is a lunatic for different reasons, but the reason for declining testosterone is not because of a crime, a plot, or correlating to a lack of masculinity, heavily masculine individuals still exist en masse, rather the average is being brought down by associated factors including average USA population increases in weight, diabetes, and of course age (See the Table below). Other factors that haven't necessarily been proven to effect us on this scale, but probably do, is the move away from meat. While strictly veganism and vegetarian demographics have declined in recent years depending on who you ask, meat-replacement markets have grown massively in the last two decades.
There is no current widespread deficiency or emergency. Even with lower Testosterone levels most males are sufficient to remain healthy, even the chart shows that all but one blip of the collected data is above the 350 mark which is considered safe.
EDIT: Looks like consumption of fat contents in meat inversely correlates with testosterone, so vegans might actually be more masculine by that definition.