He's a passable defender, but I think people get caught up in praising him for defense. They do hide him at times, but it works, so no complaining. The Westbrook chuckle got blown out of proportion. I thought he was laughing at the idiotic question from that reporter.
People keep saying that because they don't know the context. the reporter is from ESPN, she didn't ask Westbrook a question at all. She asked Durant about the steal by Curry, off Durant, that sealed game 5. She asked something like he led the league in steals the last 2 seasons do you think he's an underrated defender, and Westbrook started laughing. She wasn't even talking to him that's why people reacted the way they did, it was so obvious.
I love the guy but facts are facts, Westbrook for the series when guarded by Curry 31% 10 To's, when guarded by everyone else, 45% shooting, don't know the turnovers. He's a great player but he didn't do very well head to head with Curry. With Thompson he was able to get to the rim and draw fouls so Klay started backing off and then he hit that pullup. That's why Kerr switched it up and put Curry on him more often. He was something like 5-19 against Curry in the last 3 games, because Curry was able to stay in front without fouling so he didn't have to back off and give him the pullup.
Westbrook was a terrific defender in college, when he came into the NBA he was very good, but like many guys as his offensive stats got better and his name got bigger, his defense changed. He goes for steals now he doesn't stay home and guard his man.