Supposedly, he's actually an OK trainer and cool in person. But yeah, his theatrics are getting old. Really old. Sometimes trainers tell you, or the industry, what you, or the industry, wants to hear. Right now, "9mm all the things" is what people want to hear.
Money talks and BS walks. Those theatrics pay his bills.
.40 is still a good reliable round. Doesn't blow up Glocks unless you're a chump. Cycles more reliably than 9mm or .45. Great for silencers. Great for USPSA. Great for 3gun, when 9mm isn't dropping the "9mm calibrated" steel targets. More powerful than 9mm, even if you believe it's only equal in effectiveness.
.40 ain't going anywhere. When people get tired of weak cycling from weakly loaded cheap 9mm ammo, BTF, or as soon as 9mm fails to stop a wacko wearing a garbage can, it'll get popular again.
.40 became popular because the police were using it because it had more power, and was still high capacity. Now that they've all but dropped it, and it's been a fun to bash caliber, less shooters are trying it. It wasn't popular for very long at all. So how much demand is expected? It was never .45 kind of popular.
And newbs like cheap and easy. 9mm is cheaper and easier than .40 and .357sig.