It is not just our right, as members of humanity, to look out for our fellow man; it is our duty. If a group of people is being oppressed by their government, we, as humans, owe it to those people to do our best to help them break free of the tyranny that binds them.

Ideally, we could do that without government, but that is not often the case. Governments are an institution created by humans to serve the greater good of humanity. What is the reason to have a government in the first place? It provides protection, good, and services which would be difficult to provide for ourselves. For that reason, I don't think that a government intervening in order to help members of the group that created it (in this case, all of humanity) is a bad thing.

Government has overstepped its bounds, and becomes tyrannical and overbearing when it ceases to serve the needs of the people it encompasses. When this happens, it is the intrinsic right of the people to take the power away from the government just as they gave it in the first place.

All too often, however, the people being oppressed are unable to stand up for themselves. It is times like this when other governments must intervene. That is when it is right for government to step in. You asked the question "government of humanity" but I think most people miss is the fact that government only has power, and only exists because of humanity. Humans give power to and make up the government. Therefore, government is not exclusive from humanity, but, rather, is a subset of it. Government is meant to serve the will of humanity, and if human beings are living in fear, and with a poor standard of living, then it is the duty of government, and all of humanity, to step forward to help the oppressed.