I'm certain all of you have heard lots of talk about the European migrant crisis lately from both sides. One of the (sort of) arguments I've heard from people who are in favour of allow thousands of refugees into a country, particularly North America, is that we (not actually "we", people who lived 500 years ago) came here and if we don't want to leave, then it is obvious that we just making different rules for ourselves than we are for others. There are a few flaws with this argument; (1) we are not our ancestors, and (2) the Native Americans were slaughtered in massive numbers because of foreign immigration.
(1) It is accepted that if our parents do something immoral, we are not to blame for that immoral act. We may have had something to do with the act or gave them our support but bar that (which would make us responsible) there is zero responsibility we can take for their actions. The above is even more visibly true for people who lived hundreds of years ago even if we share their DNA.
(2) I'm sure that you all know how horrible the Europeans were during their massive migration to a different continent. Their was a massive difference in cultures between the Natives and Europeans which lead to very immediate conflict. This conflict contributed to the greatest genocide in human history. I have heard sources saying that 90% of the indigenous population were killed. Though much of this was because of disease, which was aided along by the acts of biological warfare the Europeans committed, there were still thousands killed directly because of massive immigration.
I think this is something to consider when you see this argument in the future.