Paying mortgage interest is like throwing money out of the window :-)
Additionally, there's the insane gift to banks that is the mortgage tax deduction, which significantly reduces the amount you spend on interest.
That's a particularly pointless bit of misinformation. Holding property isn't free, in general. Land is quite the liability in California unless you make enough to justify holding it. Landlords make plenty of money. Currently 750/mo (or more) for single rooms out of a house in southern california for anything decent. With AirBnB you do much better. The math is straightforward.
There is nothing that says rent has to cost more than owning.