To begin with, we may agree that consequentialism becomes suspect when it leads us to violate what we may take to be (near-)absolute human rights. That is, the utilitarian mantra of “the greatest good for the greatest number” argues that the sacrifice of the few for the good of the many is justifiable. We certainly make this argument in wartime, when soldiers, by definition, are those whose lives are potential sacrifices for the good of the many. But these days, we may be less sympathetic to similar arguments that could be made, for example, regarding enslavement. That is, a utilitarian can argue that, just as it would be ethically justified to sacrifice a comparatively small portion of the population (soldiers) for the sake of the greater good, so we can justify the loss of certain freedoms and rights of a few (slaves) if we can show that these costs are overridden by the greater benefits such slaves would provide for the larger society. If we wish to argue against the utilitarian at this point, we may do so by reaching for some notion of (near-)absolute human rights – e.g., rights to life, liberty, and the pursuit of property. If, as modern deontologists would argue, these rights exist and are (near-)absolute, then they may never be violated – for example, by turning some portion of the population into slaves – even if to do so might lead to greater pleasure and enjoyment on the part of everyone else.
Likewise, we might admire the courage of protesters – for example, during the civil rights movement of the 1960s or in more recent political protest movements around the world – who practice the nonviolent pacifism of a Gandhi or a King, sometimes with remarkable success. If we are deontologists, we would say that they are doing the right thing – even if it costs them great personal pain, and even if they are not always successful in gaining their intended political outcomes.
But many people are not always willing to accept a Kant-like absolute not to lie, for example. Sometimes, it seems quite clear that lying would be justified, for example if it were to save a life – and many lives, even more so.
In fact, Kant developed a more nuanced position in his later works, so as to make greater ethical room for deception: while we might deceive others for less than ideal reasons, as deception allows us to hide our more negative characteristics while nonetheless developing a more virtuous character, it can help us become better persons (Myskja 2008). As Kant’s own transformation suggests, whether or not deontological approaches can consistently make room for what appear to be justified and important “exceptions to the rule” is a central question for defenders of this approach.