Was colonization a good thing?

Perhaps the easiest way to understand why colonialism was so horrific is to imagine it happening in your own country now. It is invaded, conquered, and occupied by a foreign power. Existing governing institutions are dismantled and replaced by absolute rule of the colonizers. A strict hierarchy separates the colonized and the colonizer; you are treated as an inconvenient subhuman who can be abused at will. The colonists commit crimes with impunity against your people. Efforts at resistance are met with brutal reprisal, sometimes massacre. The more vividly and accurately you manage to conjure what this scenario would actually look like, the more horrified you will be by the very idea of colonialism.