Definition of cruelty (cruelty - definition of cruelty by the Free Online Dictionary) : 

cru·el·ty :

 (krl-t)n. pl. cru·el·ties 1. The quality or condition of being cruel.

2. Something, such as a cruel act or remark, that causes pain or suffering.

3. Law The infliction of physical or mental distress, especially when considered a determinant in granting a divorce.

Based on the second definition I would find it remarkable if anyone went through life without ever being cruel.  It is impossible to live and function in any society without causing pain or suffering through acts or remarks. 

Sometimes this would be inadvertent, as in the case where the person behind the register is rude to you, you don’t know that her mother just died a week ago and she is not handling it very well, hurt you say something like “your mother would be ashamed of you”  This would be amazingly cruel, but you did not know, had you know you would not have said something like that.

Other times you have to be for the person’s own good, you need to tell them their spouse is cheating on them, they really are not the greatest singers in the world, getting them to quit drugs, or alcohol, leaving them if they don’t, letting your kids spend a night in jail, so they don’t end up there for the rest of their lives.  Sometime a little cruelty is needed to save someone from longterm hurt.

Other times, you can use it in self defense, there are some people that just won’t back off until you put them in their place, often the quickest and simplest way is to say something you know is hurtful to them.  Parents often have to inflict pain on their kids, taking them to the doc for injections, putting alcohol on a wound, sending them to bed as a punishment. 

All these actions would fit the second definition.  While I think that at times everyone will be cruel, and under certain circumstances it is actually beneficial to be, I don’t think anyone should ever really enjoy it too much.  That is when the problems start, when bullying occurs, when crimes are committed and when lasting harm is done.  This is what I think most people writing for the other side are talking about.  People who enjoy being cruel and do so for fun and without good reason.

Most people can live their lives without that type of cruelty although I suspect that most at one point in their lives did something cruel and rather enjoyed it (because that person really deserved it, is usually the excuse), but most people don’t really enjoy being cruel.  Causing pain, often causes pain back and it is done as a necessity.  

But then again, research has shown that people, even ordinary people are capable of amazing amounts of cruelty if an authority figure tells them the should do it (In Repeat of Milgram’s Electric Shock Experiment), or if they are in positions of absolute power (The Stanford Prison Experiment:).  We saw this in the Abu Ghirab scandals, and has been observed at all points in time, and in all societies, from the spanish inquisition, to Cambodia’s killing fields, to Hitler’s Germany, to the Slave trade.

The truth is that if they feel justified, most people will be cruel, they will treat prostitutes, criminals and the homeless differently that they would treat other people.  Every day people walk past and ignore men and women with mental problems that live on the streets of their town. They will leave them in the cold, knowing full well that they will probably go hungry that night. 

There are people who think that it is OK to tease people who are overweight, or gay, or minorities, or just different.  There are people who will will watch someone being bulled and not do anything, who will pass someone up for a job because they think that as a minority, or a woman they will not be able to do the job. There are people that look at someone who is unattractive and will treat them badly because of it, others will do so if a person has a disability, is a minority or is in some other way not part of the mainstream culture.

The unfortunate fact is that most people will do something amazingly cruel to another human being at some point in their lives, because most people will at some point in their lives fell threatened by a situation they feel they can’t control.  They will, under those circumstances, react in ways that they may later regret, or will  come to justify because they think they are in the right to do so.  They will do this because they are human and not perfect, not because they are evil. 

Saints are never cruel, people often are.