While I disagree with the headlines wording, I agree with the statement.
Ligers are un-natural. They are the product of man cross breeding two species that would never have met in the wild. It is not their fault (the ligers) for being this way, but it is ours, and we should own up to it. All hybrids are starle, so every liger we have made has been our choice. WE choose to create these poor animals, to play God. They may not be in pain, but being a science experiment is no way to live
If you would define a freak of nature as something that cannot breed to make more of itself, then ligers are freaks. This would also mean that you consider mules to be freaks because, although mules are more common than ligers, they are also sterile and nature does not allow them to reproduce.
Ligers, the product of a lion and a tiger, are a symbol of scientific achievement. As long as no animals are harmed and ligers are able to live healthy lives, there is no reason to condemn their existence or to consider them freaks of any sort. Scientific advancement should be encouraged as long as no lives are harmed.
It is not the liger, but the ones who forced the breeding that are to blame. A liger cannot help being a liger any more than a human can help being a human. Humans do have the advantage over the liger of being able to choose what kind of human to be. To answer the question, yes, ligers are unnatural. However, let's not accuse an innocent creature of tampering with nature's laws.
So Only male ligers are sterile, females can still successfully mate with other tigers, also if you believe a liger is a freak of mature then toy believe dogs are too, pure breads attributes were made from years of forced incest and breeding, I mean pugs aren't natural, they were purposely made to look cute, or to look a certain way. Even then, tigers aren't bad in anyway, and there's a large chance they could evolve to be sterile, or science could find a way to make the males sterile, as the females already are, the source for the sterile arg is
I think the practice of mixing different species producing a hybrid like the liger is a very dangerous practice. What will stop hybridization in the future, what if one tries to mix a shark with a tornado, or a dinosaur with a diseased pitbull that lost its master in the war.