OK. Allow me the chance to explain why I am defending right-to-buy. It doesn't have anything to do with my politics generally, more on what actually works.
TL/DR: in the UK accomodation based on private renting results in a) a small, rich and lazy class and b) a poorly-housed majority class.
For those who want more detail, read on...
We will start in the 1800s, when the UK urbanised and started to look like it does now. Just about all people rented privately. In poorer areas, there were normally a strata of leases: someone at the top owning a street subletting each house, the house lessee subletting each floor, and the sublessee of the floor subletting each room. Result: squalor and overcrowding. Slum property was more profitable than property in more affluent areas (there was a fair amount of renting there too).
From about the 1850s onwards, there was increased public concern (this was probably because London was getting reall foetid and Parliament's location - in Westminster - was near some of the grottiest parts of town. They tried cleaning out houses, tried slum clearance (e.g. Shaftesbury Avenue, New Bond St), later charities tried subsided housing. Didn't make much difference. Later, people tried social housing for profit, e.g. the Peabody flats. Plenty of those still exist around London. They didn't work either because the rents were too high for the poorest.
From the 1890s onwards, local councils started providing social housing as that simply worked better. Remember that at the time it was very much a free market economy, and the UK exercised no border controls at all - anyone could come.
By 1914, I think about 80% of people rented privately, 15% were owner-occupiers and the remaining amount socially housed. I think - I read this about ten years ago and I can't remember which book I read it in.
Between the wars, and especially after WW2, councils engaged in huge compulsory purchases of private rentals. There were court cases but the landlords invariably lost. This was when councils put up the concrete high-rises etc. We say they were awful now, but they were a massive improvement on what the private sector was offering. Google "single-end tenement flat" for an example of how a huge proportion of people in Glasgow lived. Basically a one-room flat for a family.
In the meantime, the price of houses (as compared to incomes) becomes as low as it's ever been.
Skip foward to Thatcher and right-to-buy - possibly no different to what Corbyn's proposing now except that it affected publically-owned property.
Now we are heading back towards the 1800s: a reducing proportion of people owning houses, an increasing private rental market, and a hugely increasing number of people who can't afford their own home. This is not just a problem in the UK. It's across the whole Western world. I admit that it could be rough on people who have carefully built up a property portfolio. But have a thought for people who, despite their best efforts, can only find insecure housing. It's a lot rougher on them.