VALENTINE [revealing himself] Ruffian, let go that rude uncivil touch,
Thou friend of an ill fashion.
PROTEUS Valentine!
VALENTINE Thou common friend, that’s without faith or love,
For such is a friend now. Treacherous man,
Thou hast beguiled my hopes. Naught but mine eye
Could have persuaded me. Now I dare not say
I have one friend alive – thou wouldst disprove me.
Who should be trusted, when one’s right hand
Is perjured to the bosom? (5.4.61-69)
Ruffian, let go that rude uncivil touch—unhand her, you cad!!—but uncivil here is key, even more so than ruffian. This is class treachery; you are in no way acting as a gentleman. Let go of her! you’re not fit to come near her! how dare you? thou friend of an ill fashion—call yourself a friend? you’re no friend of mine. (And Proteus here is thou, formal, distant, not the intimate you.) Valentine! Well might Proteus squawk in shock and horror. But Valentine’s not going to let him speak (in some productions he might be physically preventing him from speaking). Thou common friend, that’s without faith or love, for such is a friend now. You’ve debased the very idea of what a friend might be, cynical, two-faced, faithless. Friend? you don’t know the meaning of the word any more. Treacherous man—you traitor!—thou hast beguiled my hopes. You’ve ruined everything in your betrayal and your deception, everything I’d dreamed of. (Valentine perhaps refers both to his being banished from Silvia and Milan at Proteus’s instigation, and his own disappointment in Proteus, his best friend.) Naught but mine eye could have persuaded me: if I hadn’t seen you, seen what you’ve just tried to do, with my own eyes—I wouldn’t believe it. Now I dare not say I have one friend alive—thou wouldst disprove me. If you’re the only and best friend I have—well, then, I don’t have any friends left in the world. Who should be trusted, when one’s right hand is perjured to the bosom? Being betrayed by you—it’s as if I’ve betrayed myself—you’re part of me, and you’ve played me false, hand against heart.
After his initial intervention, is Valentine saying anything to Silvia? Is he going to say anything directly about what Proteus has been saying and doing to her? Apparently not. Make it all about you, why don’t you?