Animals may provide entertainment but that doesn't mean it is right to use them. People used to think a hanging was good family entertainment but you wouldn't agree to that, would you? The animals have been treated horribly in order to make them do what the trainers want them to do ((http://www.peta.org.uk...) and (www.ringlingbeatsanimals.com/).
We should consider what the animals are made to do. When is it ever natural for a lion to sit on a barrel and wait patiently? We should let the animals show their natural behaviours, not just ones we want to see because they are 'entertaining'.
Let us ask ourselves "Does performing in a circus harm the animal?". I believe that it is possible for an animal to be used in the circus for entertainment and not be harmed. Consider the actions they do: Performing tricks, walking around, and some are just there to add a little bit of zest to the act. Also, since these animals are being kept by people, they have access to resources and medical treatment they would not normally receive in the wild. I see it not much different than keeping animals in a zoo. It is true that trainers may beat their animals to listen to them, but other forms of training are possible, such as positive reinforcement,.
Animals in circuses may have access to more medicine than in the wild but it is not like a zoo. Most zoos try to keep the animals as natural as possible but circuses don't. When is it ever natural for an elephant to do a headstand? Or for a bear to ride a bike? The British government agrees with me too as they have passed a law banning circus animals (http://www.express.co.uk...). If the government agrees, then it is unnatural and wrong.
I still don't see why it's not possible for animals to be used in a circus without harming the animal. Of course there will be times when some circuses abuse or harm their animals to get them to do something, but I don't believe the answer is a straight out ban. Perhaps some regulation is in order, but full out banning animals from circuses would remove a lot of the excitement from going to the circus. Thank you for your time, this has been a fun debate.