2) Are you being sarcastic?
3) She absolutely should, but I'm just not sure if it's relevant. Have you ever finished a sentence for a stutterer, behaved differently around physically disabled people, maybe intellectually been more thorough in conversation? Both of these things are seemingly "considerate" or "well-meaning", but they are nonetheless very condescending. If you've never been on the receiving end you might not grasp the concept, which I think is a contributor to people (typically able white men) discrediting these experiences as over-sensitivity.
4) I claim it from watching the entire video and comparing how he yielded the floor to EVERY other panelists immediately if they ended up speaking at the same time, which he did not do for her to my count 8 times, as well as treating the other non-native speaker (man) very differently than her, to rule out that factor. To your last question: That's a tough hypothetical, but if it's systemic I'm inclined to say yes. If incidental, no.
2) good point. Groups of people are never wrong, and there's certainly no selection bias going on. And it was definitely the entire room and not just some subset of the room
3) I agree, but if this is about the supposed victim, then perhaps the supposed victim should have some input.
4) I'm not sure how you can claim it is sexism. Do you know the mental state of the host? Did you consider the supposed victims explanation of why it happened that was not sexism? If a woman is ever treated differently from a man or men, is that automatically sexism?