Calvin in CONTEXT on Hebrews 1:5

5 . Thou art my Son, etc. It cannot be denied but that this was spoken of David, that is, as he sustained the person of Christ. Then the things found in this Psalm must have been shadowed forth in David, but were fully accomplished in Christ. For that he by subduing many enemies around him, enlarged the borders of his kingdom, it was some foreshadowing of the promise, “I will give thee the heathen for thine inheritance.” But how little was this in comparison with the amplitude of Christ’s kingdom, which extends from the east to the west? For the same reason David was called the son of God, having been especially chosen to perform great things; but his glory was hardly a spark, even the smallest, to that glory which shone forth in Christ, on whom the Father has imprinted his own image. So the name of Son belongs by a peculiar privilege to Christ alone, and cannot in this sense be applied to any other without profanation, for him and no other has the Father sealed.

But still the argument of the Apostle seems not to be well-grounded; for how does he maintain that Christ is superior to angels except on this ground, that he has the name of a Son? As though indeed he had not this in common with princes and those high in power, of whom it is written, “Ye are gods and the sons of the most”, (Psalm 50:6;) and as though Jeremiah had not spoken as honorably of all Israel, when he called them the firstborn of God. (Jeremiah 31:9.) They are indeed everywhere called children or sons. Besides, David calls angels the sons of God; “Who,” he says, “is like to Jehovah among the sons of God?” (Psalm 84:6.)

The answer to all this is in no way difficult. Princes are called by this name on account of a particular circumstance; as to Israel, the common grace of election is thus denoted; angels are called the sons of God as having a certain resemblance to him, because they are celestial spirits and possess some portion of divinity in their blessed immortality. But when David without any addition calls himself as the type of Christ the Son of God, he denotes something peculiar and more excellent than the honor given to angels or to princes, or even to all Israel. Otherwise it would have been an improper and absurd expression, if he was by way of excellence called the son of God, and yet had nothing more than others; for he is thus separated from all other beings. When it is said so exclusively of Christ, “Thou art my Son,” it follows that this honor does not belong to any of the angels.

If you will please note the bold type. Jeremiah 31:9 refers to Israel which is a type of the church. According to Calvin's theology, all members of the church are considered elect unless they commit apostasy. So clearly Calvin's comment on this cannot refer to the reprobate. So the common grace is "of the elect" not everyone in general. Your friend David is "prooftexting" Calvin out of context.

Soli Gloria Deo!