Williams was having a bad day. She was losing a match she should have been winning. She had been previously warned about her behavior. Yet, she cursed & threatened the line judge. The spectators were booing her behavior.
Why would the line judge risk their livelihood (cameras everywhere, you know) by making a bogus foot fault call, when Williams was losing anyway? And didn't the tournament referee (not an Asian) assess the final penalty causing the match loss?
There was no racism here, only a rattled Williams who made a foot fault & then a mouth fault.