There is a generation of pensioners who have benefitted from massive house price increases and who are now living in very expensive properties and have good pensions plus the state pension to fund it.
I generally do not think that it is fair that for example my dh's grandparents (sahm, one really minor civil servant income) had basically an extra £750,000 to downsize and spend on their retirement.
They really do not need the state pension however we have to consider doing something about that means that people may not save for their retirement 
and this problem seems particular to the baby boomer generation and it may never happen again
But if one of our goals as a country is to bring down house prices then surely 'forcing' people to sell their properties will gradually bring the prices down?