Sometimes when you see a theme, it starts to appear everywhere. That is what is happening with the ancient Greek truism that people in a crowd are more vulnerable to persuasion in a way that the individual is not. Two more instances:
The Athenian ambassadors spoke as follows: “Since the speeches are not going to happen before the majority, there is no way for us to deceive the listeners and seduce the masses once and for all with uninterrupted speech safe from cross-examination (for we know that this is the reason we have been led before the few)…
οἱ δὲ τῶν Ἀθηναίων πρέσβεις ἔλεγον τοιάδε. ἐπειδὴ οὐ πρὸς τὸ πλῆθος οἱ λόγοι γίγνονται, ὅπως δὴ μὴ ξυνεχεῖ ῥήσει οἱ πολλοὶ ἐπαγωγὰ καὶ ἀνέλεγκτα ἐσάπαξ ἀκούσαντες ἡμῶν ἀπατηθῶσιν (γιγνώσκομεν γὰρ ὅτι τοῦτο φρονεῖ ἡμῶν ἡ ἐς τοὺς ὀλίγους ἀγωγῆ)…
Thucydides 5.85, in the opening gambit of the Melian Dialogue.
And the common people marveled [at the arrival of Alcibiades and Chalcideus] and were concerned. The conspirators had arranged that the council happened to be in session, and Chalcideus and Acibiades gave speeches, saying that many more ships were on their way and concealed the naval blockade around Speiraium. So first Chios and afterward Erythrae revolted from Athens.
καὶ οἱ μὲν πολλοὶ ἐν θαύματι ἦσαν καὶ ἐκπλήξει: τοῖς δ᾽ ὀλίγοις παρεσκεύαστο ὥστε βουλήν [τε] τυχεῖν ξυλλεγομένην, καὶ γενομένων λόγων ἀπό τε τοῦ Χαλκιδέως καὶ Ἀλκιβιάδου ὡς ἄλλαι [τε] νῆες πολλαὶ προσπλέουσι καὶ τὰ περὶ τῆς πολιορκίας τῶν ἐν τῷ Σπειραίῳ νεῶν οὐ δηλωσάντων, ἀφίστανται Χῖοι καὶ αὖθις Ἐρυθραῖοι Ἀθηναίων.
Thucydides, 8.14.2, at the outset of the Ionian War.
“A person is smart. People are dumb, panicky dangerous animals.”
So Kay declares in Men in Black, using this to justify keeping the public in the dark about the existence of aliens. This is a memorable scene, but, despite ongoing debates about government secrets and a contentious presidential election, not to mention elections in Europe, that raised questions about mass participation in politics and how decisions are made, it is something of an outlier in modern discussion about democracy.
The same is not true in ancient Greece. In Athens during the 5th century BCE one of they key questions was about the fickleness of the crowds and how dangerous this could be. When a leader was both respected and responsible, such as Thucydides credits to Pericles, the system worked, but there were repeated concerns about the masses being bought by crafty politicians. (Cleon is the usual target of accusation, but Plato says something similar about Pericles in his Gorgias.) I wrote about how Aristophanes describes this problem in Clouds where he stages a debate between Just and Unjust Logos, the unjust argument declaring that his brand of speaking works better in front of a crowd. This performance, though, appears to be a reflecting an Athenian aphorism about democracy.
From Herodotus (5.97):
It seems easier to mislead the many than the one, since Cleomenes of Lacedaemon alone was not deceived, but [Aristagoras] did this to to thirty thousand Athenians.
πολλοὺς γὰρ οἶκε εἶναι εὐπετέστερον διαβάλλειν ἢν ἕνα, εἰ Κλεομένεα μὲν τὸν Λακεδαιμόνιον μοῦνον οὐκ οἷός τε ἐγενετο διαβάλλειν, τρεῖς δὲ μυριάδας Ἀθηναίων ἐποίησε τοῦτο.
The year was 500/499 and Aristagoras, tyrant of Miletus, travelled to both Sparta and Athens looking for support for the rebellion against Persia he was trying to orchestrate (the Ionian Revolt). Cleomenes, the king of Sparta, effectively told Aristagoras to pound sand. There were a multitude of reasons why Cleomenes might have done this that had nothing to do with the failure of Aristagoras to dupe him, but Herodotus pairs the failure in Sparta with the vulnerability of democracy.