Agreed, if you follow tennis a lot, this is fairly common. However, I don’t think that makes it necessarily right, but I do think this ref made too big a deal of it...and as a consequence of his actions he managed to alter the possible course of this match. Although, I think Serena would probably have lost regardless.
I really think that Serena has a valid point, why did this guy react the way he did to her, when there were other options available to him....and that he had taken when refereeing other men’s matches.
Could Serena have reacted differently to the situation, of course, but the fiery competitor in her took over...and although we might not like what that looks like, that’s almost certainly what pulls her through when the competition gets tough.