Act 2, Sc. 2, lines 442-455: Why does Hamlet choose that particular speech for the actor to recite?

Hamlet. The rugged Pyrrhus, he whose sable arms,

Black as his purpose, did the night resemble

When he lay couched in the ominous horse,

Hath now this dread and black complexion smear'd

With heraldry more dismal. Head to foot

Now is he total gules, horridly tricked

With blood of fathers, mothers, daughters, sons,

Baked and impasted with the parching streets,

That lend a tyrannous and a damned light

To their lord's murder. Roasted wrath and fire,

And thus o'ersized with coagulate gore,

With eyes like carbuncles, the hellish Pyrrhus

Old grandsire Priam seeks

So proceed you.