First of all your analogy is completely broken. In the case you describe there is an illegal act occurring. In the case of abortion, it is currently legal, even if wrongly so.
As a nation of laws when a law is unjust we are called to non-violent civil disobedience to change the law. There is a right way and wrong way to approach a problem. I have put in numerous hours and miles protesting abortion and praying in front of abortion clinics. Until today we were winning this battle...this one act has set that progress back immeasurably, which will ultimately lead to many more innocents being butchered.
I would bet most of the armchair cheerleaders for this act have never once lifted a finger (let alone gotten their butts off their chairs) to do anything about abortion.
And since you “don’t really care”, you are as responsible as Tiller.
In your religion-tinted eyes, I guess I am as responsible as Tiller. Big deal.