I'm not sure how you're defining 'cut-off' but there's no way he forced the transport truck to brake. There was ample space between the vehicles by the time he changed lanes since the motorcycle was accelerating quickly at that point.
Granted it's not recommended, but the likelihood of an experienced rider going down from a short, low wheelie like that is quite low. Saying that it is likely to lead to a pile-up and multiple deaths is hyperbole hardly worth addressing. Pile-ups almost always involve inclement weather.
Anyway, it's no more dangerous than the countless drivers I see chatting on their cell phones, disciplining their children in the back, eating lunch, etc. -- activities that probably the majority of drivers engage in at some point.