Could they block it?
Isn't the Rift basically 2 monitors strapped to the eyes with software doing the heavy lifting? How could OR block porn, or anything really, from being displayed?
If I go into a computer store and look at the monitors there, I don't feel the need to ask the sales drone "scuse me mate, does this 27 inch 1440 monitor let me watch porn?"
On a closed platform (console), yeah, they could block adult games but on an open system like a PC, trying to block something is not really an option, so it's not that the Rift is open, it's that the system powering the Rift is open, just like the legs of that chick in the porn game from Japan, wait, why the hell do I have tentacles instead of arms? WHAT?