To answer your question regarding if rebellion and revolution are ever justified, let’s look at some situations where this occurred.
In 1776, the colonists rebelled against the British. In the view of the colonists, the British refused to listen and respond to their concerns. The colonists tried peaceful protests, but things didn’t change. As the colonial actions got more intense, the British responded in even harsher tones. It reached a point, where the colonists felt revolution was the only course of action. As the Declaration of Independence stated, people must remove a government that doesn’t protect their rights.
The Civil Rights Movement is another form of rebellion. African-Americans had tried for decades to bring equality to our country. Southerners were unwilling to end slavery before the Civil War. They believed it was acceptable to enslave the Africans. After the Civil War, southerners found ways to deny the African Americans their rights. If African-Americans didn’t rebel or protest, it is very likely those rights would not have been granted. As it was, it took a huge fight to bring these rights to them. Yet, we still see examples today of racism and prejudice. Without rebellion and protest, African-Americans would still be facing an drastically unequal society.
It is important to note that killing people because they disagree with your viewpoint or opinion is not a proper course of action. To revolt for the sake of revolting isn’t acceptable. There needs to be serious and committed attempts to bring about peaceful change before resorting to violence and revolution. It isn’t okay to kill people and destroy property just because somebody disagrees with your viewpoint. If no change occurs after serious and committed dialogue, then more aggressive actions may be needed.