In the UK, they are creating human-animal embryo. 5 years ago, this would be unthinkable. I suspect you will find some proponents that were on record saying this would never happen.
And 10 years from now you might find scinetists creating human/animal hybrids. This is the danger in my opinion. Unchecked scientific research like this may one day lead to the destruction of the human race. Not to mention when Hitler's scientists was doing these experiments, the world condemned him for it.
We are "human" today but in 10 years we might be "humanimals".