'All the protagonists'?

When I was young I liked to learn facts about language. I was also a smug little git so what I liked best of all was to learn a fact that would allow me to say to people 'You're using that word wrongly'.

I'm still a smug little git but now I know that this is prescriptivism and a Bad Thing. Linguists try to avoid it, and instead describe language usage As She Really Is. For this reason, I've decided to revisit a prescriptive usage that I remember learning as a small child. This was an extra-special one for me, because it involved knowing the  etymology of a word and applying it to modern usage, and this is always a good way to make people feel stupid. (What, you don't know classical Greek? You utter ignoramus.) Yeah, I was insufferable. 

Anyway, the word for today is protagonist. The peeve that I read, all those years ago, was that you cannot say the protagonists of this play because, you great oik, there can logically be only one protagonist. That's what the word means. 

Let's find out, shall we? OED says this:

C17, from Gk 'first among actors', from protos 'first' and agonistes 'actor'. 

Now, we are discounting the fact that word meanings change over time and it's ridiculous to try to apply the literal meaning of the word to its modern usage. If we did that we'd be in no end of trouble, with lords being merely breadkeepers (the word lord was originally hlafweard, 'loaf ward') and not posh rich blokes owning all the land and wearing waxed jackets and driving SUVs. 

The question is, then, can the etymology logically lead us to the conclusion that there can only be one protagonist. Obviously the key is in protos, 'first'. And here, I think, is the problem. You could argue both ways on this one. 

You can argue that the first actor is the only one, which is the route the prescriptivists are going down. It seems pretty sensible: if I ask who was the first to walk on the moon, I want the name of Neil Armstong, as he was the first person to do that. I don't want the names of the first two people - sorry Buzz, you weren't the first. 

And there's maybe an etymological reason to argue it this way: if it is from protos, that's probably singular (my Greek is essentially non-existent, but I imagine that this is true), and so refers to just one man (it'll be masculine as well, I'll be bound - actors were blokes in those days). 

But, if you wanted, you could make an argument the other way based on use of the word first. We don't require it to be singular, in English: The first ten correct entries drawn will win a prize. That's why protagonist is often 'misused', because it doesn't seem logically restricted to one person, and indeed in plays, films etc. there often is more than one main character. 

So, happily, this seems to be a case where if you want to be a smug git and lose your friends, you are etymologically justified in doing so, and if you prefer to be a rational person and have people return your calls, you are also justified in doing so. Hooray, everyone wins!