According to Catholicism, is it sinful to physically harm abortion doctors or expectant mothers in order to prevent them from having an abortions?
The short answer is yes.
The big objection with your example is it is the mothers to be who are are going to such doctors. Should they also be the ones to be harmed or even sterilized in order to stop future abortions, your question does not address!
It is true that the ends do not justify the means as Geremia’s answer points out.
St. Thomas Aquinas states the individual does not have this right, for it remains with the state. Only the state can judge such sins and carry out sentences involving prison, mutilation or even death.
On the contrary, Augustine says (De Civ. Dei i) [Can. Quicumque percutit, caus. xxiii, qu. 8: "A man who, without exercising public authority, kills an evil-doer, shall be judged guilty of murder, and all the more, since he has dared to usurp a power which God has not given him."
I answer that, As stated above (Article 2), it is lawful to kill an evildoer in so far as it is directed to the welfare of the whole community, so that it belongs to him alone who has charge of the community's welfare. Thus it belongs to a physician to cut off a decayed limb, when he has been entrusted with the care of the health of the whole body. Now the care of the common good is entrusted to persons of rank having public authority: wherefore they alone, and not private individuals, can lawfully put evildoers to death. - Question 64. Murder
If St. Thomas says that it is unlawful for the individual to execute the guilty, it follows that the individual can not harm that same said evil doer. Besides in our present day, he is protected by law as abortion is not considered a sin or crime by many modern governments.
No one has the right (privilege) to take the law into his own hands.
It is the law that allows abortion to flourish that must be changed in order to stop a doctor from accomplishing such crimes. Until then the doctor is protected by the law of the state.
Since many states allow abortion, the question of how to stop this crime in our modern society is very complex to say the least.
The main point here is that society has to be sanctified. And that main work: a lot of work. It must always start with individuals and work outwards.
We must be willing to do penance and mortifications in order the our modern societies will repeal the laws allowing abortion. We need many more St. John Vianneys in order to bring holiness back into the Church and society in general. This is the way to really stop abortions.
To end the practice of abortion; both contraception and pornography must also vanish from being mainstream in every day life. Hearts and minds must renewed and purified, otherwise abortion will simply continue as it is.
Yes, we have our work cut out for us.
13 Let everyone be subject to the governing authorities, for there is no authority except that which God has established. The authorities that exist have been established by God. 2 Consequently, whoever rebels against the authority is rebelling against what God has instituted, and those who do so will bring judgment on themselves. 3 For rulers hold no terror for those who do right, but for those who do wrong. Do you want to be free from fear of the one in authority? Then do what is right and you will be commended. 4 For the one in authority is God’s servant for your good. But if you do wrong, be afraid, for rulers do not bear the sword for no reason. They are God’s servants, agents of wrath to bring punishment on the wrongdoer. 5 Therefore, it is necessary to submit to the authorities, not only because of possible punishment but also as a matter of conscience. - Submission to Governing Authorities
Besides, no pope or council has or ever will officially accept the idea that doing harm to an abortion doctor is sinless, since it stops abortions. Let’s do our part by doing penance, mortifications and prayer in order to convert the sinner.
Nowhere does the teaching magisterium of the Church allows us to exercise our personal ideologies outside established laws of legitimate governments. The Church does not and will not permit individualistic anarchism to rule.
Individualist anarchism refers to several traditions of thought within the anarchist movement that emphasize the individual and his will over external determinants such as groups, society, traditions and ideological systems. Individualist anarchism is not a single philosophy, but it refers to a group of individualistic philosophies that sometimes are in conflict. Benjamin Tucker, a famous 19th century individualist anarchist, held that "if the individual has the right to govern himself, all external government is tyranny".
Open season on abortion doctors is not a Catholic social teaching that I have heard about!
If the Catholic Church were to allow the faithful to physically harm or mutilate a physician in order to stop him from preforming abortions, it would be widely known. No such principles exist in Catholic thought, tradition, philosophy or theology. End of argument!