It seems rather fallacious to suggest that anything legal is moral when it comes to business.
Morality is a mix of individual belief, faith, and community norms. My point is that what people find immoral here is pretty specious and of a rather isolated community.
But there is nothing about petty human infighting that deserves praise. It's a huge (and unavoidable) waste of time. In an ideal world, employee poaching would be prevented by providing a better working environment and compensation. We don't live in an ideal world, sadly.