Those are (I presume) referring to instances where the colonised were 'bad', and the colonisers have done 'good' (to put it in simplistic terms). I agree that there are such instances! There are also instances where the colonised were 'good', and the colonisers have done 'bad'. Or, if the presence of any 'bad'ness is enough to lead one to be an appropriate target for colonisation, there are also instances where the colonisers' civilisation was 'bad'. How many of each? Well, obviously my position is that colonisers overall do much more harm than good. Maybe that's not true, but you won't disprove it by mentioning a couple of good things that they've done.
(There are also instances where keepers of slaves have done good, but that doesn't mean we condone slavery.)