The existence of a PATENTS file is not the point of contention here: it’s its content what marks the difference. Such simplifications caricaturize the issue at hand.
As I said in the article I linked to (which I highly suggest you read, as these questions are answered there), a patent grant is good: ASLv2, MPL, CDDL, EPL all give patent grants with weak patent retaliation clauses, i.e. if you use X and accuse X, you lose the patent grants for X.
Facebook is in a whole different level with its strong patent retaliation clause. Not even Oracle — known for its predatory practices, unpopular opinions and attempts to capitalise on open source — is with Facebook on this one.