Be kind whenever possible. It is always possible. - Dalai Lama
Compassion is often held by Buddhists to be the most fundamental of the emotions, since if you feel compassion for the sufferings of others, everything else (like being kind) will naturally follow. Studies have been done to find out how people can treat each other horribly (e.g., torture, murder, etc.). The one element which seems absolutely necessary in the manufacture of an evil person is for them to fail to identify with their victims. Once you don't have to worry about those mirror neurons telling you that your victim is suffering, you can treat them as you wish (if you are interested in this subject, I highly recommend a book by Phil Zimbardo called The Lucifer Effect). It's very unfortunate, but making ordinary people into horribly evil creatures is not that difficult. Denying this reality is like denying the truth of your own suffering - it might help you avoid thinking about unpleasant things now, but it's nevertheless a rejection of the truth and will ultimately get in the way of understanding. For example, people tend to think of the holocaust as something perpetuated by evil monsters instead of regular folk. As a consequence, they think that people like themselves could never do such things. But they are quite wrong about this, but their false confidence prevents them from seeing the danger or taking steps to avoid it.
A while ago, a photo album showing nazi guards at some of the worst concentration camps relaxing and having fun was released (see http://www.ushmm.org/museum/exhibit/online/ssalbum/?content=2). People expressed amazement that guards who had spent the whole morning killing people could take off for a picnic at lunch where they laughed, sang songs and picked berries with their fellow executioners. It's not surprising, though, if you consider that these people are perfectly normal in most respects. They suffer, they make plans, they have friends and lovers, etc. The difference between them and us if that they learned not to feel compassion for a certain segment of the population and this allowed them to act as they did. The first line of defense against such behavior is to develop your ability to feel compassion. If I can feel the pain of another, then I will not want to inflict more pain on him. And we have to be very careful restricting our compassion only to certain people, because we know where this can lead...
In fact, the more you practice your compassion, the more you realize that even jerks are deserving of our help. Research shows that the first step in treating others badly is a failure to identify with their suffering. One of the most common ways people do this is to assign blame to the sufferer. If I can say someone is in a bad position because of their own action, then I am much more likely to feel that person does not deserve assistance. If you look for this pattern in your conversations with people, you will spot it again and again.
What's wrong with that? There are two basic truths you will come to realize if you continue to practice meditation. First, the fact that someone creates their own problems does not mean that these are not problems or that we don't have a responsibility to help them. Thinking that way, more often than not, is just a quick and dirty technique for rationalizing our failure to help. I will risk a political analogy here: Conservatives like to emphasize the virtues of self reliance and, to be sure, there is much to praise about this attribute. But sometimes it seems to go too far. For example, I once had a conversation with a conservative friend about retirement. He was in favor of doing away with the current system of social security and instead just letting everyone save for their own retirement. I pointed out that many people will not save appropriately and thus will end up destitute when it comes time to retire. "Well, that's their own fault!" he said, as if that ended the conversation. But I replied, "Yes, it surely is. But are you willing to let them starve in the streets because they were stupid?" He wasn't quite sure what to say, because the convenient mechanism of blame had prevented him from really thinking through all the consequences of his proposed policy. Now, I am NOT trying to influence your politics in favor of social security. But if we want to change a system that has a huge impact on lots of people, then we have an ethical obligation to carefully consider the consequences to those impacted. It's terrible that people are often so stupid and we should do everything we can to prevent stupidity. However, we will probably never prevent stupidity entirely and being stupid should not be a death sentence.
The second thing you come to realize is that we are ALL guilty of causing our own suffering in various ways. The undisciplined mind is constantly thinking things that cause suffering. Someone who fails to save adequately for retirement has done something to cause their own suffering, but then someone who constantly doubts their own self worth is thinking something that causes their own suffering. Therefore, the difference between you and those you might say "cause their own problems" is one of degree, not of kind. This is really the key insight of Buddhism - that while suffering is the one universal of human existence, it's a problem we create for ourselves. Thus, it's a problem we have the power to overcome.
Ok, so spend another 20 minutes on compassion meditation: those in dire shape, family & friends, neutral people, difficult people. If you find yourself really depressed towards the end, you can always take the last minute or so to do some loving kindness meditation, which helps you end the meditation session on a high note...:)