If he had killed a mass murderer of preschoolers, I doubt anyone would be on his case.
The difference is that the law currently protects preschoolers. The law is wrong not to protect the unborn. This case raises the question of when should we give up on the rule of law and take matters into our own hands.
A better analogy would not be a mass murderer operating outside the law, but say government approved euthanasia of preschoolers with parental consent to reduce overpopulation and global warming. The murder of preschoolers even with parental consent should strike a chord in our consciences that would result in many more Scott's giving up on the rule of law and taking action.
As long as elections are free, and abortion remains not a large enough issue to overthrow the current judicial rulings, then the blood of the unborn will be on the nation's hands.
Because I view the abortion laws as wrong, I don't think I could vote to convict this guy. But doesn't failing to do so, open up an argument that says anyone else can take action against the system for any perceived failing of the system.
I think we have to go back to the Declaration of Independence for guidance. "Prudence, indeed, will dictate that governments long established should not be changed for light and transient causes"; and accordingly all experience hath shown that mankind are more disposed to suffer, while evils are sufferable, than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same object evinces a design to reduce them under absolute despotism, it is their right, it is their duty, to throw off such government, and to provide new guards for their future security.
The problem I keep coming back to, is that there remains a means of redress through elections. We are represented. It's just that the will of the people is not strong enough to overthrow the judiciary rulings that fail to protect the rights of the unborn children.
So overthowing government would not fix this, as the people's will has to change. Would a war against abortion doctors change the people's will? Probably not. And if not, then more abortion doctors would simply rise up to replace them. So what will change the will of the people?