Rom 3:8 And not rather, (as we be slanderously reported, and as some affirm that we say,) Let us do evil, that good may come? whose damnation is just.
The apostle Paul says in Romans that those who “do evil that good make come” are worthy of condemnation (damnation). As Christians, one should not vote for John McCain, who supports killing babies whose mothers have been raped or whose parents are related, such that Obama, who supports killing babies for any reason whatsoever, would not win.
Likewise, we should never rape another human being, even if it would save the whole world. God never authorizes us to make moral compromises.
Mat 16:26 For what is a man profited, if he shall gain the whole world, and lose his own soul? or what shall a man give in exchange for his soul?
Predicting the future is a hard task. We can never know what harms or evils might be brought into the world through our compromises, but we can know for certain that never doing evil will always be the right thing.
We do not vote for McCain/Hitler (fill in your politician) so Obama/Stalin won’t win.
We do not kill an innocent baby so that baby doesn’t grow up in an unloving environment or so some woman does not have to live with reminders of traumatic events.
We do not rob from the young to pay for the health care of the old. (Remember God labeled even a 10% flat tax as an evilly oppressive tax rate. 1Sa 8:15)
We do not forbid trade with foreigners such that natives will have higher paying jobs.
We should not illegalize smoking so people might live longer.
We should not do evil that good may come.
reality is not optional 
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I think this article is too narrow.
If a psycho enters a classroom, to kill all children,
I think it is morally responsible to shoot the psycho.
I agree. If something evil is about to happen, you may need to take drastic action; in that case, said action is not really “evil”, since it has a good purpose.
There’s nothing evil about banning cigarettes! What are you talking about??? Don’t lump something good in with several evil things to sugar-coat the evil thing and make the good thing look bad!
Also, you need to weigh the two acts and choose “the lesser of two evils” — in other words, if something super-evil is about to happen (like your example of a guy who’s about to “go all Columbine on you”), you may need to commit a somewhat-smaller act of evil to prevent it. Just like you should not cause/allow a huge evil to occur just to prevent a small evil from happening — for example, suppose someone says that he will commit suicide or kill someone else if you do not kill a whole bunch of other people. Well, if you cannot restrain the person from committing his threatened atrocity, it would surely be better to allow him or one other person to be killed, rather than bumping off a whole bunch of innocents.
Or suppose a guy tells a lady that he is terribly depressed and is planning to commit suicide. She therefore caringly asks him if there is anything she can do to help him so that he will not commit this act (remember, it is widely believed that God does not approve of suicide), and he replies that if she will have sex with him, he will feel better. So what’s she supposed to do — just allow him to die, or save his life by spreading her legs for him? The Bible does not allow for reality. And the vast majority of “believers” just complacently “go with the flow” and do not try to help anyone out in situations like this because their religious christenings tell then that ANY sin is wrong, no matter how good the end-result would be. God isn’t fair — he should allow “impossible” situations to occur in the first place.