I've seen the episode in question, and Top Gear also spoke very highly of the car in parts, and said it's the first electric car that a person might want to own. Also, anyone who watches the show knows they speak honestly and make fun of just about everything, including electric cars.
Personally I'm a fan of Tesla and am looking forward to the Model S being released next year. But, I'm also a fan of Top Gear and this lawsuit is really just making Tesla and Elon Musk look like a bunch of cry babies about a bad review.
Welcome to the automotive world Elon.