As a Ranald fan , I have to disagree with some statements here.
I'm pretty sure Ranald would sooner bless he bandits than the bandit hunters. He is the god of theft, deception and anarchy, bandits fit right in. True he is the god of revolutionaries, but only while they are revolting, once they become the government Ranald is at best non-hostile to any power structure, he is never supporting of it.
And a Ranaldian bandit would say that his lot are vigilantes absolutely. Didn't they pay that farmer to sleep in his barn last night? They are just taking from the rich (read anyone who travels the roads that looks to be worth robing) and giving to the poor (their friends and family). Raland is a fundamentally anti-social in all his guises, though mostly harmlessly so and even at his worst he is better than the alternative.
No and no. First no: Ranald is very much not a backer of abusive violence. He is exclusively pacifist in any guise other than the protector. A Ranaaldite bandit may justify things in stupid ways to appease the protector, but Ranald himself is very much the most interventionist order god (except for, maybe, the lady?), so if he disagrees he shows it. These types may exist, but they would displease him. Besides, there is a god of violent thefts allready, so unless you are Robin Hood or genuinelly believe you are protecting people
Second no. Ranald is fundamendally social. A god doesnt only has facets, he also has his tenets, and one of his tenets ( There is no honour among thieves, yet trust in your brothers and sisters, for there is honor among Ranaldans ) is very social. His protector facets is also explicitly about protecting the weak from the strong, not merely fighting the strong (on that matter, the bandit mentioned would be the strong in that equation) He may be the kind of person who would support anarchy based on the actual beliefs of anarchy (as opposed to the pop culture ones), but in setting he is very much apolitical.
In sort, he isn't a chucklefuck who only eats popcorn, he seems to have actual ideals.
In some of the few excerpts from IC Ranaldite texts we have in Tome of Salvation, Ranald is explicitly described as being a bandit while mortal.
Ranald the Nightcrawler doesn't approve of unnecessary violence. What's necessary is very much in the eye of the beholder. Violence necessary to accomplish a crime might well be acceptable to him.
Worshippers of a god have very wide latitude to construe what that god's doctrines are, and the Warhammer gods grant them favour anyway, even if it's contradictory with beliefs held by others of their cultists they also favour.
The Ranald that Mathilde worships might have a Protector aspect who approves of that, but the Ranald that others worship may well not, just as the Jeramism Ranaldite sub-cult believes that He created all the other gods as a cosmic joke and so actually is the ultimate god.
I think (haven't read any Warhammer lore, just going off the wiki, so correct me if I am wrong) Ranald is shown to be a Robin Hood style bandit, which is a very different thing from a bandit as most people understand one. It is as different as the protagonists of One Piece are from pirates. Its more in line with what people consider a Rogue than an actual violent, oppressive, bullying bandit.
Ranald is also explicitly anti-violent crime. Any and all Ranaldian violence must be done in the guise of the Protector (or I guess the gambler, if you are a poor soldier that is used as a pawn and just wants the luck to survive, but that is something entirely different)
As for the latitude you proclaim... that is the one thing I know not enough Warhammer lore to dispute, so eh, if that one is real, maybe my points about that bandit and the anti-violrent bandit thingy above are incorrect.
Edit:
It seems I got ninjaed by new arguments while formulating my reply above. Let's have a go.
I didn't say that they were shaped by a consensus. And even if they were it wouldn't matter in the way you're suggesting. I'm saying that Warhammer gods can be self-contradictory when looked at from the perspective of two different worshippers. The worshippers' expectations partially define what experience they have of the god. This isn't absolute, but it's why there can be priests in communion with a Sigmar that they believe and grants them spells on the basis that he's the one and only god, while other Sigmarite priests receive spells from Sigmar, King of the Gods, and others are granted miracles by Sigmar who is one god amongst equals in the pantheon. All those versions of Sigmar would be equally correct, because the worshipper in question believes that who Sigmar is, and the concept of Sigmar in the warp is broad enough to encompass all of them.
There isn't an IC consensus that recognises the true nature of the gods. As I've quoted to you before, no one outside the College accepts the true nature of the gods. And the fact that they believe something else doesn't make it true about the general nature of warp entities. It just means that the god acts to and through them as if it's true. Belief doesn't determine reality at large, it's not consensus reality. It just determines the character and so actions of warp entities. Sigmar-The-One-True-God isn't actually the only god, but he acts as if he is as through that subset of Sigmar's Cult.
If that what you mean, it may well be that gods do not actually care that much about details they consider unimportant, such as theophysics and dogma minutiae, as long as the bulk of their actual ideals is carried out.
Indeed Ranald is not bothered by non-oppressive power structures , which is not the same as saying he supports them. He is non-hostile, neutral. Ranald also does not like unnecessary violence, but he is not fundamentally opposed to that either. Ranald says 'use a stiletto not a sword', not 'take up pacifist crimes'.
A Ranald worshiping bandit who worships say the gambler as part of his spree of violent crimes is about as far from the dictates of Ranald as Mathilde Weber who uses the gifts of Ranald to prop up the authority of the Empire and the Colleges and fight the enemies of mankind. Both are combining things that under Ranald's umbrella, theft deception and risk taking, with things he is neutral on, banditry and sporting legitimate authority. Would Ranald suddenly abandon Mathilde if she was bandit hunting? I do not think so, but neither would it abandon a hypothetical bandit priest turning his power against her.
No, that bandit is not equally far from Mathilde, cuz Ranald does not hold every commandment as equal in letter. He seems to be pretty much a "protect the weakest is my foremost priority" god in ideals, and a " be cheeky, smart, and daring" in means. Ideals trump means.
Mathilde doesn't prop up up institutions, she props up institutions that are actually of benefit to the weaker man. That is a huge difference for Ranald, I think.