Is it true that people who bully are insecure?

I believe so. Most bullies only bully others to feel better about themselves. Bullies are most of the time insecure, and think that bringing others down will make them feel better and be better, which is obviously not the case. They may have problems at home or something that not many know about and take their anger, frustration, grief or even sadness out on others. Bullies also may bully because they are jealous of you or somebody and feel that they need to take it out on someone, which may unfortunately be you. If you are a bully, think twice next time before taking it out on others.

Sometimes yes, people who bully others are weak too. So they tend to pick up on someone that they find weaker and less protected than them because they want to gain some sort of power for all time they felt powerless about things happening to them. They release self-hatred and insecurities to people as a form of a coping mechanism to battle their inner insecurities / demons and that is what we called as projection. So remember, if you are being bullied, It's not you being called like that. They are simply releasing their insecurities of themselves to other people.

A lot of the time people who bully are projecting their problems onto the people around them. Sometimes they are made to feel so low that they bring others down to feel a bit more highly of themselves. In addition, some people may bully people to gain validation from others around them especially if they see these people as higher than them. It's important to understand that the bully is the one with the issue and that there is underlying issue with them and not the victim. A lot of the time the bully has low self esteem and feels that bringing other's self esteem down makes them feel less alone.

Hmmm this depends on the person I think. Some people would choose to bully since no one was there to correct their action since they have started. Others may be doing it because, like what you have said, are insecure. In the end, it's not easy to group a person or put a definitive label on them without knowing them properly. They may seem to be like that but sometimes they continue to be like that because of the label and acting to maintain it. Once again, it is different for different people. This is just my opinion on it.