[Of those philosophers who dispute the utility of learning grammar], Pyrrho is recorded to have been constantly reading Homeric poetry, a thing he would not have done if he did not recognize that it was useful and that, for that reason, studying grammar is compulsory. And Epicurus has been caught red-handed snatching the best of his beliefs from the poets.
ὧν ὁ μὲν Πύρρων ἱστορεῖται τὴν ῾Ομηρικὴν διὰ παντὸς ποίησιν ἀναγινώσκων, μὴ ἄν ποτε τοῦτο ποιήσας εἴπερ μὴ ἐγίνωσκεν αὐτὴν χρησίμην καὶ διὰ τοῦτο τὴν γραμματικὴν ἀναγκαίαν, ὁ δὲ ᾿Επίκουρος φωρᾶται τὰ κράτιστα τῶν δογμάτων παρὰ ποιητῶν ἀνηρπακώς• τόν τε γὰρ ὅρον τοῦ μεγέθους τῶν
288.2-4
“But anyone who investigates it will find that the ideas of poets are much worse than common sense of regular men.”
ἂν δὲ καὶ ἐξετάσῃ τις, πολλῷ χείρονα τῆς τῶν ἰδιωτῶν ὑπολήψεως εὑρήσει τὰ
τῶν ποιητῶν.
For his last point he is veering towards the opinion of Plato that poets are no guide to any other skill.
For example when founding a city, you need someone to frame the laws, but as Plato says.
What city claims that you (Homer) were a good law-giver or had been of any use to them?
σὲ δὲ τίς αἰτιᾶται πόλις νομοθέτην ἀγαθὸν γεγονέναι καὶ σφᾶς ὠφεληκέναι;
Plato Republic 599e