The thing is... All biological parents can notice their kid's crappy behaviour. My son is only 19 months and I notice when he's having a day of not listening because it's exhausting for me - the one trying to keep him in line. But biological parents that are lazy and have stepparents in the household aren't impacted because the stepkid has someone to direct the behaviour at - the stepparent. I promise you, he notices. He's just not impacted by it because YOU are the target. 

Oh, he knows all right. But if he acknowledges it, then he has to DO something about it. And that’s too hard. After all, you’re the only one suffering. He and demon spawn are fine. 

You have to make his inaction and sh!t parenting hurt more. 

Sounds like laziness and conflict avoidance to me.  There's no way that your husband doesn't notice his kid's bad behavior.  He notices it and doesn't want to deal with it.  My DH does the same thing; fortunately his kids aren't completely out of control.  At least when I point things out and tell him to deal with it, he will.  But then 5 minutes later he looks all sad and says that he doesn't like to be mean to them.  I just roll my eyes and tell him that parenting is not "being mean," and it would be meaner to let them grow up to be uncivilized terrors.  So many of these men seem to act just the same.

My DH has always known what a POS his son is. 

I have the same problem. It's better now that SD13 is older and SD15 doesn't talk to him any longer but I lived this, sometimes still do. 

So here's my suggestions.

Stop trying to talk to your DH about it. Does no good and focuses him on you. Ignore! It gets easier with time. Leave the room unless you are doing something you really need to do. If you don't leave, firmly and nicely tell kid to leave and you won't ask again. This worked for me if I sounded like a teacher and esp if I was in a kitchen with hot things and knives zero excuses. Still amazingly have to tell YSD to knock off messing around in kitchen NOW.

Second. That cap gun or anything noisy disappears one thing at a time. If you don't want to throw it our, then find your own hiding place for it. 

Sometimes just make time for yourself. DH too busy? Even though SS is being ok? Go do something else with no prior announcement...just like hey heading out for a little while see you later! 

They don’t want conflict with the kid because then “the kid won’t want to be here.”

And they “only want the kid to be happy” and that means no punishment because punishment won’t make them happy. And this ignores the fact isn’t not their job to make the kid happy, it’s their job to be a parent. 

But now there is another parent because “we are a team.” But woe to the “bonus” parent if the kid isn’t happy, then you aren’t part of the fun team. 

Personally I think it’s called “bonus” parents because it’s like a game and they get extra points for pissing off another adult. 

And there’s no way the dad wants to confront the bio mom. Because, even if the mom doesn’t have primary custody legally, they have primary custody mentally in the dads head and she could end up with the kids at any moment. 

So you gotta keep the kids and the bio mom happy and the step parent is just supposed to be part of that support squad. How dare you question the rules of the game. 

Can you record your SS insulting you? Then when your DuH says he didn't hear it, reply with "Here you go, then" and play the insult back. Force him to notice, force him to hear, force him to take action.

I read somewhere once that certain people aren't bothered by a dripping faucet.. and some people... it drives wild.  (I recall it tended to be women who fell into the latter category).

In a way, I see stepkids as the dripping faucets in our household.  The bio parent is the one that the dripping doesn't bother and the stepparent is going out of their mind. 

I think with step parents.. we are starting from a lower level of patience... so "anything".. even minor and subtle hits us hard.  Bioparents are a bit more able to let the smaller things roll.. or even not notice them much at all.

There are lots of reasons why a bio-parent can and will "ignore" things.

1.  If they are NCP, they may feel they get precious little time with their child already and don't want to spend it fighting.

2.  If they are NCP they may feel that they don't have the abiltiy to control things as much due to less time with the child.

3.  NCP parents may feel that they are at a disadvantage because the stakes with the other bio parent could cause them to lose custody.. or cost them more money if they are hauled into court .. so rocking the boat is "harder" and has high risks (your wife isn't gonna take you to court for an annoyance.. your EX might)

4.  Biology... it's easier for a bio parent to unconditionally love their child which means focusing more on positives than negatives. and honestly not even notice the dripping.

5. conflict avoidance... an fairly natural trait in many people.

Sometimes as a stepparent we need to be more vocal and specific when there are issues.. and perhap not make mountains out of EVERY mole hill.  focus on changing things over time instead of all at once.  Also disengaging to an extent can be effective because no one is saying you have to necessarily put yourself at risk constantly.  It should be clear though that if your spouse "trusts you to care for their child.. they should trust your decisions regarding consequences for negative actions as well."in other words.. you should be free to correct the child..(not physically obviously).. and if you aren't.. well.. your spouse needs to take full control and leave you out of it.

My partner is aware of many traits of his kids, but not all. He hadnt noticed that our whole household was being upended to cater to OSS's schedule as basically a tool of manipulation by BM. I mean he'd noticed BMs behaviour but not that it was making OSS entitled. I pointed it out and he saw it.  Im thankful I dont get a lot of defensiveness on SOs part. He doens't want to raise an entitled and selfish son. 

Luckily my SD isn't THAT bad, but my DH would let her get away with murder even if she was. You know stepkids have special privileges. We can tell our bio kids to be quiet, go play somewhere, etc. but GOD FORBID we say that to a skid (I just commented on another post about this exact same thing... the special treatment). My DH always wanted SD to have fun here, to be the fun dad at the fun house. He was afraid she wouldn't want to come back if she wasn't having fun or was punished in any way. Well that came back to bite him in the @$$ because as soon as SD got the chance, she chose to stay with BM full time. He put up with all that crap for nothing lol

Sounds like DH, or the great I am just to stressed to deal with that. Or I have a headache I can't talk about it right now. (then goes and hides)

These men need classes, and we all needs glasses full of wine.....

A bit late to the party but I just wanted to say how much I laughed at "oh he's just tired " I used to hear that ALL THE TIME. As if just that simple sentence makes everything ok.

I don't think they are blind to it. My ex openly admitted that as he only got eow he wasn't going to spend it making his dd upset by telling her off, she could do what she wanted when she wanted and he wasn't going to apologise for that. I think it's called Disney daddying.