Despite the popularity of many moral nihilists now and in the past, such as Nietzsche, the vast majority of people throughout history have believed in some form of morality. It is a deeply human trait to instinctively classify our experiences, whether our choices or anything else, as good, bad, evil, immoral, charitable, loving, positive, negative, just, unjust, etc. Even before the nihilist can stop himself, those moral sentiments have already appeared, and even the most immoral people usually believe their bad actions are justified, or they simply ignore their conscience until it builds to the point of personal ruination.
With this innate moral compass that all people share, everyone is also capable of having their own attitudes and intellectual beliefs about morality. These primarily derive from the way we understand and interpret the moral sentiments our conscience gives us, and the way we decide to act on them. Through reason, we can expand our morality by implications, religious belief and what we know about human behavior to include things such as culpability, imputability, concupiscence, law, and myriad other concepts. However, reason also gives us the ability to "rationalize" our choices - meaning, we can think up seemingly-reasonable reasons to excuse or justify our choices even though those excuses defy conscience and/or the rational moral framework we believe in. Often, this moral framework is influenced by the excuses we build up over time, a filter through which we experience the world and by which we make choices. This creates an attitude, a way of looking at the world and ourselves that usually determines (though not beyond free will) our moral compass.
One of the most common attitudes that every person is susceptible to is what I call "justification by utility", or to use the philosophical term, utilitarianism. A fundamental principle of objective morality, of a morality independent of the arbitrary preference of the individual person, a morality attested to by the essential logic of philosophy and lived (even if refuted intellectually) by almost every person, is that an action which is objectively moral or immoral is so regardless of the situation or condition of the person. Now, this only involves the moral quality of the action or thing itself, involving the inherent philosophical morality of them; the guilt of the individual is determined by their internal consent and knowledge. But regardless of the person's internal condition, an immoral act is immoral - regardless. Theft, the stealing of one person's private property by another person, is immoral, violating the fundamental human right to private property. But if a severely impoverished or ignorant person steals food, is it still immoral? Yes, the theft itself is still wrong - but the individual's guilt is lessened.
This is an essential principle of morality which utilitarianism rejects. Utilitarianism is the attitude that the morality of an action, separate from the culpability of the actor, is determined by its practical result. Now, the standard by which the practical result is judged to be good or bad is arbitrary, and depends on the placement of another moral belief system atop utilitarianism (such as the affixation of liberal consensus relativism to it featured in the philosophy of desire utilitarianism). But regardless, with this attitude, only the utility of an action determines its morality.
Usually, proponents of utilitarianism would say that actions such as lying, stealing or killing are wrong, since they most often lead to more negative results than positive. Lying creates an unsustainable fantasy, endangers one's reputation and is essentially uncreative, never leading to productive results for the common good. But, what if doing something wrong, such as lying, stealing or killing, does in fact lead to great positive result? This is the true loophole within the attitude (as it is not truly a rational philosophy due to its rejection of constant objective morality) of utilitarianism, and it was the excuse used to justify the Holocaust, the dropping of two atomic bombs on Japan, abortion, euthanasia, assisted suicide, stem cell research, contraception - the list is almost infinite.
The opposite of the utilitarian attitude is an attitude of integrity. This, as a virtue, is naturally difficult, the main reason few people have it. Integrity is adhering to what is right and true regardless of one's situation, one's difficulty, or even the possibility of better results by using an immoral means. Justifying the ends by the means derives from a lack of integrity, a weakness of character where one chooses to succumb to the temptation to sin - the immoral means - and justifies it with the possibility of positive ends. It is a test of the heart: what do you love - ease, productivity and pleasure, or truth, goodness and hope? For without the light of hope, and the faithful life of the hopeful person, willing to undergo the trials of suffering - without the certainty that, in the end, no end is worth a wrong means, no result attained by immoral means will last, and salvation will come - there is only darkness.