This is written for
alchemyangel351, who wanted an exploration of whether the Weasleys were really models of non-prejudice. I assumed you meant towards the Muggles, but my apologies if you wanted me to approach prejudice towards other aspects.
“There is no prejudice so strong as that which arises from a fancied exemption from all prejudice.”
- William Hazlitt
Humans are always flawed, and J. K. Rowling has taken no exception to her characters. Take a garner at the extremes with Dumbledore and Voldemort. No matter if the goal is pure good or pure evil, nature makes it impossible to maintain such an extreme. Dumbledore has his weakness of love, if you will, which drives him to secrecy and manipulation. Voldemort is blinded with the pettiness of revenge and still adheres to decorum - as per the duel in GoF - despite being labeled evil. The Weasley family is no exception.
What is prejudice? If one takes it to be a preconceived notion about a person before getting to know them, everyone is prejudiced. A person who acts like an arse at a first meeting will be presumed to be an arse at a second meeting. A person who dresses in rags will appear to be poor. One is judged by everything besides the blatant - color, sex, the physical aspects of the human being. One is judged by how one speaks and how one acts - one doesn’t like putting a name to relationships, but they are a series of judgments. Once someone has passed a person's “test”, they have graduated to the next level of trust.
But this is diverging from the topic at hand, which is the prejudice of the Weasleys. Their accusation lies with their mollycoddling Muggles. Whereas Hagrid treats Muggles with a sort of vague disdain (the comments about the lunacy of parking meters, etc.) and the Malfoys with sneering disgust, the Weasleys are nothing short of … piteous towards them?
Arthur is hands-down fascinated with their inability to live apart from magic. Ron has comic books about Martin Miggs, Percy dates a Muggleborn and Fred and George acknowledge the usefulness of Muggle lock-picking. Molly is sympathetic, in a “poor dears” sort of way. They all feel that the reign of the Dark Lord against Muggles was evil. They are on the whole outspoken against the bigotry of Pureblood superiority. All of them - there’s no reason to assume any of the children are not - are comfortable with Muggleborns, but only stray into confusion when directly placed with Muggles themselves (such as in GoF at the World Cup where Arthur panics about Muggle money).
Thus, any blood prejudice concerning witches and wizards is excluded - the Weasleys are very Hufflepuff in this. However, one cannot deny the variation in treatment towards the Muggles and, though this could be a discrepancy in only Ron, towards Squibs. The real test of the state of non-prejudice for the Weasleys is their treatment of the non-magical.
Arthur is simply confounded by the Muggle ability to get by without magic. They are hindered in a way he simply cannot imagine, and yet they thrive. He loves their alternatives, and, working in the Misuse of Muggle Artifacts department, works to help them from being exploited by what he views as the stronger of the two - the magical world. This attitude firmly lodges in some peoples’ minds as obvious prejudice. And in a way it is true - Muggles are treated differently. That they are treated in their favor is irrelevant - it is different.
The real world parallel that immediately arises is prejudice concerning intellectual ability. The fact is, prejudice is a product of difference. Muggles are indeed different from the Wizarding World. They cannot do magic. One cannot get around that fact. If one treats a Muggle like one would a wizard, such as throwing a baby to one and expecting a levitation spell to prevent the baby from smashing on the ground (purely hypothetically, of course), the Muggle would be unable to do it. If one needed an army to fight against Voldemort, one would not go looking for Muggle infantry (Assuming the Dark Arts shield from physical attack). Similarly, one doesn’t think that voting an idiot into presidency is a smart move. One does not put a mentally challenged person in charge of nuclear weapons. Muggles do not have the same capabilities as witches and wizards - they cannot be treated as though they were witches and wizards.
So returning to Arthur’s “pity” towards Muggles, look at this: there will always be witches and wizards trying to exploit the Muggles. It is human nature to be greedy, it is human nature to take from those weaker than oneself - it is human nature to not be perfect. There are several alternatives within the Ministry concerning the protection of Muggles. One: excise total equality with them. Let them fight back themselves, because of course they are capable of taking on magical powers. Two: excise total protection of them, putting them in cages so that they can be monitored and kept from the bad guys - letting them roam around like helpless babes is just cruel. Three: excise a modicum of fairness and make it so that there are some protection against Muggles and penalties against the wizards and witches who exploit them.
How should society deal with those not mentally competent? Do they not also offer other things (as do Muggles)? Pity - yes pity - may not be kind, but they are different. Indifference is cruel. To not build ramps for people in wheelchairs, saying that it’s mollycoddling is ludicrous. Similarly, helping Muggles out isn’t a display of outrageous prejudice.
This brings the essay to the apex of its point: the Weasleys act in the best way one can when dealing with an inferior race. One cannot treat them “equally”. Pure equality is a denial of the parts that make one special, unique. For the Weasleys to treat Muggles like Muggles, they would have to be Muggles.
Conclusively, yes, the Weasleys do have their prejudice against the Muggles. All witches and wizards have some form or prejudice against them - they cannot have no opinion (unless one of them somehow doesn’t know that Muggles exist, which is a pretty big stretch, but an interesting idea). But their treatment of Muggles, with tolerance, admiration and a maternal protection, is about as good as it gets.
An interesting thought to leave any reader of this essay with, though: in his own way - despite his words - Voldemort is probably to closest thing to treating the Muggles with equality there is. He is threatened by their power, he wants them acknowledged within the Wizarding world and he does not care that them are magically weaker. He kills them all the same.
Any errors are completely mine. All criticisms and comments are welcome.