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

sometimes people think hurting others will take away their pain. or the pain they are feeling is so harsh that they think the pain they will feel after hurting someone will feel better.

they may feel like it'll make themselves feel better if they don't feel that they're the only ones going through it, or they may think that it will cause people to understand their pain & empathize. but it is not the way.

Weakness. A great bunch of weakness and insecurity. Sadly, a lot of people feel like their own life gets less miserable if only they can drag others on their level or even further down. It can even give them some feeling of power and might to massage their ego, but it's probably just them being scared of feeling like they're alone with the pain.

Everyone reacts to pain differently, and for some people, that reaction is lashing out. To want others to feel how they feel, or simply not understanding that the reason they are hurting others is because they are hurting. Sometimes pain makes people upset, and it's easy to hurt others when you're upset. It's not necessarily that they wish to, but it does happen. It can be a sort of relief, to push your pain on to someone else. That doesn't mean that it's a positive thing, but it is understandable.

This is a hard concept to understand. This person must feel a lot of pain and resentment. They must be upset with them self and not know how to deal with it; therefore, they hurt other people to avoid their own pain.

Possibly because they want others to feel their pain. Their pain might've been caused by society and they wanted everyone to feel the same pain they put this person through.

Sometimes people who are in a lot of pain want other people to understand how they are feeling by making them feel pain as well. They feel that others need to feel the same pain as they are.

Because they have no where else to inflict this pain. It's a common thing people do nowadays as they become so isolated in their own problems. To see someone in the same boat as them almost comforts them. Doesn't mean that it is right however.

Oftentimes when persons are angry, they want others to be angry too. Likewise when they are sad or hurt. This is the reason the adage 'Misery loves company' holds true. It sometimes makes persons feel better when others are in pain if they are in pain. It differs for everyone. but have you ever been hurt or angry and because of that you say mean or hurtful things to hurt others? That is how persons in pain may feel.

Some people who are so clouded in their misery resent other for their happiness. They feel alone and isolated. They feel the world is unjust. They want to see that they are not alone. That others are miserable too. These people need compassion more than anyone.