BTL: Sensible financial planning or selfish avarice?

[JonChalk]

So, with all of the lovely PH advice about having 4 or 6 or 93 BTLs being the only way to ensure massive financial security in the future, do you believe that:

BTL is socially and economically viable for ever, is perfectly sensible financial planning for your retirement and does no on else any harm,

or

BTL is a pernicious, selfish disease designed to promote your own financial wellbeing over the good of the country, for ever perpetuating and worsening the unaffordability of housing at the lower end of the market?