Nym and Pistol suddenly righteous?

[Miss Plum]

Ha, it may be a while before I ever see an answer here, but I'll throw out the question anyway:

In Act I scene iii, Falstaff orders Nym and Pistol each to take some phony love letters to Mistresses Ford and Page. They both refuse to pander for him, even though, as we've seen previously, they are men of little conscience (robbing and ridiculing Slender) and they relish their image as drunken bullies. They've just watched Falstaff fire Bardolph, so they know he disposes of his followers at will.

Why do they refuse to carry the love letters for Falstaff?

[Charles Darnay]

I was tempted to let this question pass into obscurity in the hopes to quell any existence of this Falstaff-murdering play....but Shakespeare discussion is still Shakespeare discussion.

Two things to consider in regards to your question. First, did Nym, Pistol, and Bardolph rob Slender? The answer is "probably" but it is never confirmed. Regardless, Nym and Pistol are known as braggarts, rouges, and cowards - so robbing Simple is certainly in their characters.

The more important point is the reason for refusing to deliver the letter. I do not thin it is because of any moral reasons.

FALSTAFF
Go bear thou
this letter to Mistress Page; and thou this to
Mistress Ford: we will thrive, lads, we will thrive.
PISTOL
Shall I Sir Pandarus of Troy become,
And by my side wear steel? then, Lucifer take all!
NYM
I will run no base humour: here, take the
humour-letter: I will keep the havior of reputation.
FALSTAFF
[To ROBIN] Hold, sirrah, bear you these letters tightly;
Sail like my pinnace to these golden shores.
Rogues, hence, avaunt! vanish like hailstones, go;
Trudge, plod away o' the hoof; seek shelter, pack!
Falstaff will learn the humour of the age,
French thrift, you rogues; myself and skirted page.
Exeunt FALSTAFF and ROBIN

PISTOL
Let vultures gripe thy guts! for gourd and fullam holds,
And high and low beguiles the rich and poor:
Tester I'll have in pouch when thou shalt lack,
Base Phrygian Turk!
NYM
I have operations which be humours of revenge.

Nym and Pistol do not want to be put in the position of messenger servants. The idea of carrying letters is base not because it is unmoral but because it is beneath them. As we see in both Henry IV part 2 and Henry V, these are characters who seek to rise above their station (this is why they associate themselves with Falstaff.) They think they are better than they are and therefore refuse to be messengers.

Nym's plan for revenge is a result of Falstaff casting them out, not a desire to preserve the dignity of the women involved.

Such are just my thoughts.