I am impressed Nate that you seem not to refer to translations when struggling with a sentence.
Here is the immediate context (9.23), which I perhaps should have included:
καίτοι προστάται μὲν ὑμεῖς ἑβδομήκοντ᾽ ἔτη καὶ τρία τῶν Ἑλλήνων ἐγένεσθε, προστάται δὲ τριάκονθ᾽ ἑνὸς δέοντα Λακεδαιμόνιοι: ἴσχυσαν δέ τι καὶ Θηβαῖοι τουτουσὶ τοὺς τελευταίους χρόνους μετὰ τὴν ἐν Λεύκτροις μάχην. ἀλλ᾽ ὅμως οὔθ᾽ ὑμῖν οὔτε Θηβαίοις οὔτε Λακεδαιμονίοις οὐδεπώποτ᾽, ὦ ἄνδρες Ἀθηναῖοι, συνεχωρήθη τοῦθ᾽ ὑπὸ τῶν Ἑλλήνων, ποιεῖν ὅ τι βούλοισθε, οὐδὲ πολλοῦ δεῖ:
And the Perseus translation:
Yet your hegemony in Greece lasted seventy-five years, that of Sparta twenty-nine, and in these later times Thebes too gained some sort of authority after the battle of Leuctra. But neither to you nor to the Thebans nor to the Lacedaemonians did the Greeks ever yet, men of Athens, concede the right of unrestricted action, or anything like it.
So there are a bunch of datives in the previous sentences flowing from the verb συνεχωρήθη ("was conceded (to)".
Then we get to 9.24.
Davies writes in his notes: "τοῦτο μέν, adverbial as in § 11; here answered by καὶ πάλιν." καὶ πάλιν begins the next sentence. That's a whole 'nother can of worms, so I'll bracket it for now. Here's the whole of the 9.24 passage if you want to look at it: http://www.perseus.tufts.edu/hopper/tex ... ction%3D24
But what of ἐδόκουν? Now as I write this, the light bulb is going on. I think the subject is the Athenians of that time: they seemed to be behaving not within measure. And the datives early in the sentence flow from πολεμεῖν!
So my gloss would be:
ἀλλὰ τοῦτο μὲν ὑμῖν,
but [τοῦτο μὲν] to you
μᾶλλον δὲ τοῖς τότ᾽ οὖσιν Ἀθηναίοις,
and more to the Athenians being/living then,
ἐπειδή τισιν οὐ μετρίως ἐδόκουν προσφέρεσθαι,
when they seemed to be behaving towards some not within measure
πάντες ᾤοντο δεῖν,
all thought it necessary,
καὶ οἱ μηδὲν ἐγκαλεῖν ἔχοντες αὐτοῖς,
even those not accusing them,
μετὰ τῶν ἠδικημένων πολεμεῖν
to fight with those who had been injured
So, to close the circle:πολεμεῖν τοῖς τότ᾽ οὖσιν Ἀθηναίοις
The same Athenians who ἐδόκουν...
As for μηδὲν, I actually think οὐδέν would work just as well since there were actual peoples fighting without accusing, and
the whole idea seems concessive. But I guess Demosthenes is emphasizing the uniformity of Greek behavior and so opts for μηδὲν.