There is no doubt that tennis is rife with sexism, and Serena Williams has definitely been a victim - the issue of her catsuit at Roland Garros being a recent example. That being said, I just don't see it with what happened yesterday.
Her coach was issued a warning for coaching - the rule is that coaches can't coach from the stands - the umpire wasn't accusing Serena of cheating, but he was penalizing her because a team member broke the rules (something which her coach later admitted to.) Now you can make the argument that this rule isn't evenly enforced, but that's hardly unique in any sport, and I don't think you can expect the ump at the moment of enforcement to go through his mental rolodex and consult how often a rule is enforced; what's more, it would be bizarre to criticize an official for actually enforcing a rule. Criticize the rule if you like, but don't criticize an official for enforcing it.
Next, Serena received another warning for breaking her racket - pretty standard issue, something players regularly face. However, because of the previous warning, she was docked a point.
Following this, Serena embarked on a lengthy diatribe against the official, demanding that he apologize (something that no official, in any sport, has ever done - and why would he, given that he was enforcing a written rule?) She even said that he would never officiate another one of her matches (an incredibly arrogant thing to say, although perhaps excusable given the heat of the moment.) She then went next level and called him a 'thief'. A lot of the media seem to be downplaying this remark, but in my opinion that's a pretty inflammatory remark to make against an official whose job is based on impartiality. After pretty patiently sitting through the outburst, the ump assessed her a game penalty, which is what happens for a third violation. It should also be noted at this point, that Serena has previous with this kind of thing (she has previously called an ump a loser and threatened a linesperson with physical harm.)
I keep hearing that male players get away with similar abuse, but I'm not sure I remember too many players going off an official the way Serena did. The ones that spring to mind (McEnroe, Tarango and Fognini) were given match misconducts, which is far more severe than what Williams was given.
Finally, this is the second time that Serena has managed to upstage what should've been a great moment for a first-time Slam winner - Stosur in 2011, and Osaka last night.