I think he could've gotten his point across without making her turn around and then putting his face behind her ass.
The argumentative method of rather than saying and doing what you believe and instead doing and saying what you are opposed to, is always weak and usually a great way to shoot yourself in the foot.
That being said. I agree 100% with making Meta Employees feel uncomfortable with their own products.
If you judge this video without any kind of context, then yes he is a weirdo harassing strangers who are just trying to go about their day. The point is that these glasses enable this weird behavior, and the people he's filming are (ostensibly) part of that system.