You don't respond well to differing points of view do you? That's not good.
You have no idea whether a refrain from interracial breeding is a slippery slope. You have no idea how many racists would start looking for something else to make them happy. And anyone can throw out the 'slippery slope' into anything...in any direction.
No, mixed race people are not the problem. But their mixed race nature is a serious problem, for them and then, in some cases, for others around them. People like you however, might be the biggest problem since you're quite happy to promote non-consensual human experimentation and then justify it with platitudes and appeal to establishment dogma. Racists are a secondary, much less harmful problem since most of them wouldn't fabricate people who, by all known variables, would predictably be unhappy and generally disturbed, at a minimum. Today's racists are also not necessarily "finding" anyone. They're usually assimilationist at best and segregationist at worst. Society has changed thereby changing racists but mixed race people continue to suffer as demonstrated by legitimate studies (due, according to you, to a cripplingly toxic mindset). If you think your perceived account of the ones you knew trumps that then I'm not sure there's much I can tell you. Enjoy your opinions, no matter how unfounded. I'll be sure to let the other mixed race people I meet know that they need to change their cripplingly toxic mindset. I'm sure the studies will have radically different results from that point on. Mixed race people need to take on this burden so that your opinions about the right side of history can be championed.
Not believing there's a correct side of history makes you morally bankrupt in the eyes of most of humanity, whether you like it or not. There's not even anything to argue here; you don't have to have a heart, but you'll continue to be seen as a reprehensible person by almost everyone in the world. I find it baffling you're even trying to debate ethics while acting like the biggest both-sidesing moral relativist in existence.
And on the topic of history, yes, we do know that one thing leads to another when intolerance is tolerated. There are endless examples of this. But it's also not my job to rehash basic history to you. Just keep eating up your alternative facts, it's a good look.
Being mixed race, or as you put it, a "half breed," cannot be established as the cause behind psychiatrist illness in said people vs. the way some of society treats them. None of the sources you list claim to prove that because they aren't complete and total drivel such as what you're spouting.
I mean it's common sense: nobody decides without some sort of feedback from others that they're outsiders and should feel like shit about themselves. Where do you think a person's sense of identity even comes from? I'm honestly not sure if you're just profoundly ignorant or depressingly half baked for implying such bunk.
Calling it "non-consensual human experimentation" is just fucking rich. Say that to literally anyone you aren't talking to from behind a screen, they won't be able to keep a straight face. Mixed race people have existed for aeons, and by this logic, you'd have to decry all human reproduction as being "experimentation." You can if you want to, but you'll look like even more of a clown.
And no, I can't speak for all mixed race people. I'm sure many are miserable. But neither can you. And marginalized populations in general are incredibly miserable. That doesn't mean they should all stop reproducing and off themselves. What a pathetic and unhappy mindset that must be to have.
Anyway, enjoy your profound and self-inflicted misery. I'm going to go spend my time with people who don't wallow in their perceived inherent victimhood over being born. Maybe I'll even have conversations with them that aren't laced with fallacies and bad logic.