Sentiment detection in text, for example, is not emotion detection. That's not a rebuttal.
As an example of what I mean, you can feed a NYT news article written by a journalist experiencing regret, or boredom, or elation, due to events at home, while writing it -- and it won't pick up a thing. But it may pick up a valid sentiment of outrage, which was intended by the author as the desired effect upon the reader, but which was not once felt as an emotion by the author while writing it.
Semantic detection is far easier because the author of text generally tries to communicate a sentiment, consciously, in their text, and text is intended to have fairly unambiguous meaning. Neither is generally true of emotions on the face.
And nowhere did I say emotions only exist in static images. Of course they are communicated through voice, video, etc. -- I don't know how anyone could think otherwise.
Your initial post argued about it being difficult to detect emotion given just a single frame, then concluded that "any AI products designed to supposedly recognize emotions are necessarily snake oil".
And I stand by the snake oil comment for the reasons stated, with the state of AI and emotions research today.
I'm not saying it can never be done, but that we would need major breakthroughs in both.
Sentiment detection continues to be an entirely different area of research.
Please consult the current state of AI before giving an a priori rebuttal. Emotions can also be detected in text, voice and video, not just in static images. Sentiment detection in text is widely used.
The premise of the article is valid, whenever AI systems are being deployed they need to be ethically vetted, but the writing is superficial and 'too emotional'.