What Is Wrong With The World - Animals kept in captivity

Okay so I was reading the Metro on my (ninety minute long - just saying) train journey to school today, when I came across the daily 'In Focus' section. Today it was about animals and their zoo environment.

I personally think it's wrong to part animals from their natural environments just to be shoved into tiny cages and gawped at by humans. And the Metro article just backed up my opinions.

"The two-year-old giraffe, Marius, was killed to avoid inbreeding - there were already enough giraffes with similar genes in European zoos. His death - he was shot in the head with a bolt gun. Despite offers to provide a new home for him, the Danish zoo went ahead and euthanized the animal. Not only did it stand by its decision, Copenhagen Zoo used Marius's carcass to perform a public post-mortem examination. His remains were cut up in front of an audience containing many children before he was fed to the zoo's lions."

I personally think that this is a horrible thing to do. Even though an online petition to save Marius generated almost 30,000 signatures, the zoo blatantly refused to change their minds or accept any offers (despite the fact that one person actually offered £400,000). 

I completely disagree with the keeping of animals in zoos because, really, there is no benefit. The only thing they show is depressed animals, and children don't learn anything about how the animals would be naturally. Because, naturally, lions don't pace back and forth, and polar bears don't walk around in circles over and over again.

Copenhagan Zoo also murdered a lioness and her four cubs because they shared "genetic defects caused by inbreeding." Now don't get me wrong, I'm not an animal rights extremist like the nutters at Peta, but even so I don't think it is right to just casually kill animals like that, let alone whole families. But then again, I don't even like people killing spiders, so I'm probably not the best unbiased person to write this post.

Even so, it's pretty sick to keep an animal in captivity and deprive them of their normal needs like hunting, raising their cubs naturally, and most of all having the freedom to roam about.

Am I right?