"Those Dutch were the descendents of violent thugs who stole the land and enslaved the people. They have no legal or moral right to the land.
Because modernity won. And the Dutch lost."
Ah, but now here's the rub - is there a legal or moral right to return that land to the descendants of the people who had it before that, when they in turn were also the descendants of violent thugs who stole the land and enslaved the people?
Take, for example, the area around Johannesburg and Pretoria (the former Transvaal), seized by Afrikaaner (Dutch) settlers in the 1830s at the expense of the Northern Ndebele (a.k.a. Matebele) people, who were forced across the Limpopo river into what is now Zimbabwe. Sounds like it should be fair enough for them to make a land claim and take back what was theirs from the invaders, right?
Except: The Matebele tribe was founded by Mzilikazi, a former Lieutenant of Shaka Zulu. He and his people lived in Zulu territory well to the southeast, until he quarrelled with Shaka, rebelled, and fled - initially north into Mozambique, then west into the lands that the Afrikaaners would later take. Arriving there, he slaughtered the local tribes and engaged in a scorched earth tactic to ensure that even the lands not actually used by his own tribe in the area could not support other tribes. When did this happen? The 1820s.
The fact that only a decade or so passed between successive conquests obviously makes this an unusual case, but the fact remains: go far enough back, and there's not a single piece of land anywhere that wasn't at some point taken forcibly from someone by someone else. And while I have great sympathy for the notion that if you buy or inherit stolen property you can't complain when its former owner comes to claim it, things are considerably less cut and dried when that former owner in turn got the property by theft, or inherited it from someone who did.
At a certain point you just have to draw a line under history, admit that nobody really has a "legitimate" claim to ownership of the land, and try to establish the rule of law so that in future land is no longer taken from people against their will.