Why would someone who is already in pain wish to inflict it upon others?

They might be experiencing so much pain, they don't know anything else. It could control them and make them think hurting others is the answer, when it is not. It could simply just be too much to handle.

Some instances, inflicting pain onto other makes people feel as they do. This allows them to feel that someone can connect to the pain they felt as well.

For many that have been hurt have also been manipulated. Especially when those inflicting pain are close friends or family and can sometimes be confused with love or appropriate treatment given the circumstances. For these people who have been hurt and manipulated in this way, it is less of questioning why they wish to inflict harm upon others and more what makes them inflict pain upon others. The answer could be as simple as missing out of some key relationship factors to have been taught that is how to treat other people. #monkeyseemonkeydo

People have different ways of coping with pain, and some people who experience pain don't know how to cope effectively, which often means they will lash out as a result. I generally believe that most do not intend for others to feel the pain that they do, again because lashing out is their coping strategy. However there are no doubt some individuals who feel 'well I'm suffering, so why shouldn't they?', almost in the same way that bullies are often victims of bullying themselves.

they probably don’t know how to cope with the pain that they are in. It’s never okay to hurt others because you are, but a lot of people cope by taking their pain out onto someone else

They want others to know the pain that they are feeling . These people do this because they feel the world is inbalance and they would believe that its unfair that they are the only one suffering. Rather then seek help they simply just choose to harm the people around them

Some people may find it as a way of ignoring their own pain, to cope. However, it's not helpful. Because then people will make others feel the same thing they've been through. Some may be even jealous of others' happiness which is not very acceptable. If someone you know tries to inflict their pain on someone else, talk to them to sort out the issue or at least inform them of their mistake.

Well, I think that the person wants to be fully understood. He/she wishes to inflict pain upon others so they would fully understand him/her , how they feel, how much it really hurts them and what it's like to be them. Personally, I think a person wouldn't fully understand what someone is actually going through if they have never felt it. Maybe they will understand some parts of it but they won't fully understand the situation. But when someone has already been through that experience, then they are likely to understand the situation better. These are just my thoughts, I'm not a professional or anything.

This may happen because the person hopes to get rid of their pain by inflciting it on others. Though this is not right, in the moment they are doing what they feel is the only way to get a release from the pain they are feeling on the inside. Sometimes people don't know healthy ways to cope with how they are feeling. This may be due to lack of education on coping or they may have been in situations that taught them bad coping skills. This is not an excuse for their behavior though and they should be held accountable for their actions.

They don't know how else to feel better about themselves. Sometimes it's easier to bring someone else down than to lift yourself up.