I think the idea is that nobody would prefer to rent if given a choice, and that everybody could afford to own if not for the presence of landlords in the market.
Possibly but that is not the main argument. The main argument is about the lesser of two evils. Do we want to prioritize the open market of SFH ownership, or do we want to prioritize (maximize) the number of people who can own a SFH. Banning multiple SFH ownership would target the latter, with the tradeoff of a restrictive ownership path for wealthy individuals.
