You're absolutely right - they should. I WILL give credit to my ex - he did pay his child support every month. He thought I was robbing him blind at $125/month per child - three of them when he was making WAY more money than I was. It just so happened that at the time I was new to world of legal secretary and working for a domestic relations attorney so I was privy to what other fathers in my ex's financial bracket were paying and my ex was getting off E-A-S-Y. The kids remember him sometimes handing me checks and asking me to hold them a few days until his paycheck was deposited ... and he'd be out of town with his sleazy 2nd wife in FL or NV or some such place. I WILL give him credit for voluntarily paying child support beyond their respective 18th birthday until their high school graduation. He divorced and remarried that wench 5 or 6 times before it was all over with for good. She married someone else and shortly after she died. He went on to marry another far worse wench who totally OWNS him. Our children now consider the first stepmother (whom they hated) a walk in the park compared to the current demon he's married.
Fast forward a few decades and my children are 49, 47 and 42 ... and their father has informed them first that he never loved them and doesn't know why ... then recently after a plea from my youngest, informed them that he loves them but will not participate in any functions of their lives, will not stay in touch with them or see them ... he loves his wife and she's good to him (which is to say she'll drink with him and is a good piece of ass). So at this point, I have three very hurt children on my hands ... one of them a near basket case.
When a woman gives birth ... she does NOT spit out a DIY manual along with the child. It's learn as you go and it's a lifetime relationship. It doesn't end on their 18th birthday. There is no such thing as a PERFECT PARENT - you do the best you can, you love them, you nurture them, them chide them, ground them, you get angry with them, you get so frustrated sometimes you call them by 3 or 4 different names before you finally get the name right ... but above all you love them ... they laugh today and still wonder who "Carol Ann" is ... and I have absolutely no idea...just a name I spat out in frustration.
I've known a few divorced couples, where each ex-partner sounded just like you. Very bitter and hateful toward the other ex, always ranting on and on about some greatly-exaggerated, if not outright fabricated, accounts of the other's alleges vices. And they wonder why they have fewer friends than they used to have. They don't get how tiresome and unpleasant it is to hear that petty behavior, or just how it makes them appear to others.
And of course, you're blaming your ex for your children's problems, probably not even giving the slightest thought to what effect your constant badmouthing of, and hatred toward their father has surely had on them. That, also, is pretty much typical of what I've seen in other broken families where this sort of behavior has prevailed.
It's truly a sad and tragic thing for children, when their parents hate each other more than they love their children.