Earlier quoted context omitted.
Are you not an investor in that situation? The person who wants to own a house to actually live in is the only one not being an investor.
I think the concern is local investors keep the money in the local economy, whereas 'foreign' investors are extracting value from the local community.
I think this is only possible when large scale investors 'corner the market' by buying up a large percentage of homes in a given area. They can then control the rents because there is little competition.
On the other hand, if nearly every rental home is owned by a separate investor then each owner is competing with all the other small investors for tenants. They have competition and might be forced to keep the rents lower.