Ok, that could support a genetic relationship to certain kinds of mental illness, but hardly makes a statement about the character traits of the population as a whole. You said
"There appears to be a genetic basis for many types of mental illness, alcohol dependence, and a host of other things."
Care to support the alcohol comment? Because I have 'googled' quite the opposite. And what host of other things are you speaking of?
OK, I Googled "genetic basis of addiction" and got this as the top hit:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3506170/
"For example, peer influences and family environment are most important for exposure and initial pattern of use, whereas genetic factors and psychopathology play a more salient role in the transition to problematic use.2"
"Evidence from family, adoption, and twin studies converges on the relevance of genetic factors in the development of addictions including SUDs and gambling.7–13 Weighted mean heritabilities for addictions computed from several studies of large cohorts of twins are shown in Fig. 1.14 Heritability is lowest for hallucinogens (0.39) and highest for cocaine (0.72)."
and it goes on and on in a lot of boring detail. So that's addiction in general.
Here's the first link I came to doing a similar search on alcohol addiction:
http://www.medicaldaily.com/genetic-basis-alcohol-dependence-240850
Again, I'm not arguing that every single one of these genetic links will pan out, but it seems to me that you have yourself in a position where you must argue that none of them can possibly pan out. From the perspective of the argument you were seeking in the OP, I don't think that that is a winning debate strategy.
This is important as that is exactly the kind of "data" that gives some folks justification to treat other races as inferior.
Showing that certain populations are at higher risk for schizophrenia says nothing about a particular individuals character trait in that population.
And frankly that is what lies at the heart of racism. Assigning character traits to an individual BASED ON HIS PHYSICAL CHARACTERISTICS. A broad brush painting.
In that case, you have an easy job. If the person you are arguing with believes that every single indigenous person in Manetoba is an alcoholic, then you can clearly refute them. The key thing in such an argument would be to get them to explicitly say that. If they have a negative opinion of indigenous people in general, but acknowledge that there are plenty of individuals who are different, then that strategy will not work. It wasn't clear from your original post
Yes, it is not a terribly unreasonable hypothesis that there could be differences, but is there evidence for "negative" traits.
We're talking about an explicit and exclusive genetic component that leads to negative behavior.
Why wouldn't there be traits that you regard as negative? For one thing your judgement and the judgement of natural selection are not necessarily the same. For another there are clearly negative traits that are associated with, some, populations. This only matters if you are trying to construct an argument that there can be no such negative genetic component. You have a much much easier argument if you just try to show that nobody has done the studies in this specific population, and hence the racists views are unevidenced assumptions rather than categorically wrong.
Make no mistake, I hear too often, "Indians are drunks", not poor people are drunks, or country people are all drunks. Or in case of the gentleman in the opening post, we need to thin those indians out. Not we need to thin those poor people out, or we need to thin those protestant people out.
This is an erroneous implication that genetically there is something wrong, inferior, or generally caustic about "indians", and they all stereotypically have these traits.
People talk imprecisely. Racial groups and cultural groups often map to the same people. One could say Indians are drunks and mean the racial group, or the cultural group.... probably most of the time it maps to the same people. Your poor people comment intrigues me. You seem to be saying that if there was a clearly identifiable group of poor people for whome poverty, lack of work, lack of education, alcoholism, high birth rate, low life expectency and family breakup were endemic and handed down generationally, people wouldn't view them negatively. I'm not at all sure that that is the case. In the UK at least, such people living on welfare in housing provided by the government are quite often the subject of negative attitudes.
In general terms, sure it is possible, why would genetics limit itself to determining hair colour or the height of cheekbones. We're talking about and overall set of negative traits. First Nations folks lived for thousands of years in North America without needing Europeans to "fix" them. I struggle to see how, if they were genetically predisposed to negative traits, they survived so long and have such a rich history.
Hell, culturally they have a much better religion that treats the earth with much more respect than the European Christian mentality has.
That is more like the sort of argument you should make. Having said that, the world in which they are living in now is completely different with different stresses, availability of alcohol, food, and welfare. It doesn't seem obvious to me that a culture and a cluster of genetic traits that suited one environment must necessarily suit another.