1)  Sometimes colonialism is justified in dire situations.  When a nation is collapsing and will be destroyed if some other nation doesn't come in and bring stucture colonialism is acceptable.  Colonialism can be good if the type of government being forced into another nation gives the people power or gives equality; especially if the new government is replacing a system that just doesn't work and is causing more bad things to happen than good.

2)  If there was a nation about to collapse and another nation swooped in and enforced some sort of other culture, that the natives of the collapsing nation might disagree with, it would at least be saved from extinction or complete destruction.  Another scenario is that if there was a ruler running a nation into the ground, starving the people, even killing the people; another country coming in and knocking out the old ways might not be so bad.