I don't thinbk the FA overeacted.
The FA was within their right to show the passeneger was refusing to follow the directions of a FA while on the ground. Why think the passenger would follow FA instructions once in the air?
The person was sitting in an exit row where you are required to show you speak and understand directions given in English and are able to carry out emergency procedures. If you refuse to listen to what is being said then you have no right to sit there. If you speak English and refuse to follow FA instructions your rights to be on the plane are probably limited.