Message for OP's husband :
Please try to set aside this whole 'just the way it is' thing. That's a phrase that applies to tides, gravity and volcanoes, but it does not apply to humans. We have free will and we are, within our limitations, how we choose to be. You know this already, perhaps not consciously, but you do know this. You chose to move out from your parental home at the earliest possible time, because you wanted to live in clean surroundings and to be able to get up in the mornings to work for your living. (Good choices, BTW.) Meanwhile, your parents were choosing to live in filthy surroundings and to drink late into the night. Nobody was forcing them to do this. This was not/is not 'just the way they are' - it is how they chose/choose to be.
At 16 and having to pay your own way meant you would have had far less disposable income than if you had stayed with your parents, so that was not an easy choice for you to make. And yet you made it. You still saw your parents, but on your terms - at football, in restaurants, dinner at their house. You continued to choose to live your life as you saw fit, not how they saw fit. You chose to be a separate person, of a separate household.
Fast forward, you are now married with children. You live a considerable distance from your parents, so frequency of contact is limited. Now, there may be reasons which have nothing to do with your parents as to WHY you live so far from them; but regardless, desire to be in constant contact with them DID NOT OVERRIDE those reasons. You (and your wife) made a choice.
You must be able to see how rude they choose to be to your wife; your WIFE, the person you chose to be with for the rest of your life, forsaking all others, the mother of your children, your companion, your lover. The question is, why do you CHOOSE to allow them to behave towards her (and by extension, you) in this way? They are in your (you and OP's) house. They are guests, and the norm is for guests to be polite and appreciative of their hosts. It may be that because the OP is an adult, you feel she will put up with this intense social assault by your parents for you; to please you and make you happy. (And does their behaviour please you and make you happy, husband of OP? I sincerely doubt it. By telling yourself that it is 'just the way it is' you are coping with something you feel you must endure. But why must you?)
Now, your daughter is nine. Your mother told her she wanted to beat her mother badly enough to put her mother in the hospital. She's NINE. She does not have an adult's resilience, nor an adult's ability to step back and see your mother for what she is. You've taught your daughter to love your mother, and this makes her vulnerable to your mother's behaviour. She cannot hope to reconcile the conflicting thoughts, fears and emotions that your mothers vindictive hostility will have aroused in your daughter's mind.
You might feel for yourself that you can endure your parents, that you have an obligation to them (you don't, BTW). You have chosen to inflict them on your wife for over a decade, and she is now at the end of her very long tether. She has put up with them for love of you, but you really need to stop this torture, for the love of her. And you really need to think seriously about the effect your parents are having on your children. They are YOUR responsibility; and frankly - you're shirking. Bad enough that you treat your wife this way, she always has the choice to leave you. No such choice exists for your children. They need you and your wife to protect them from a pretty toxic pair of individuals. You've told your wife that you think the kids benefit from your parents visits. Can you be specific about how they benefit? Actually put that 'benefit' into words? I sincerely doubt it. Because there is no benefit. I'm sorry, but your parents are horrible people. You got out as soon as you could. So why are you thrusting your wife and children into the path of their steamroller? It's unkind. Downright cruel. Please, change your choice over this matter. Because you know you can. And you must know that you should.