Your argument in the post up-thread appears to be that because the Native Americans did not cultivate or make use of the land in any Western sense, they have no claim to ownership. The Kant quote attempts to repudiate this by stating that it makes no difference whether we consider the Native Americans' use of the land to be ineffective: their deprivation of it is still an injustice and, when it comes to injustice, the ends cannot justify the means.

I don't find Kant's position at all convincing, mostly because the two parties' understandings of the concept of "ownership" were not mutually intelligible (possession vs usufruction). However, the quote does have relevance to your post.