1) Acknowledge that SM has an opinion. Go on to say that it doesn't matter to anyone but her and dad.
2) Call SM "dad's wife". This is taken as an insult by some who got married so they get the title of SM and can have their lives wrapped up in other people's kids lives.
3) Admit you're happy your kids don't have a SM. How else will they be raised properly and who else will be there to show your kids all the extra love they so desperately need?
4) Admit you're happy about not being a SM. I've been told that shows that I don't have a lot of value - apparently I need to go back to #2 and find a man with kids so that I can wrap my life up in those children instead of my own.
5) Say you won't talk to dad's wife, I mean SM, sorry, about your kids. Or that another mom doesn't have to do so. If you don't realize she is raising your kids in that house and she knows what is going on you're out of your gourd and should have no problem talking to her.
6) Raise your kids as you see fit. The only time you're actually free to do this without judgement if when you are still married to the father of your children. So, those SMs who have SKs but are married to your kids dad, you are free to do whatever you like with your kids.
7) Say you want your kids with you instead of a SM when dad isn't around. Any mom who does this is just trying to come in between sm and her Sks and it has nothing at all to do with the fact that childhood is short, divorce cuts the time you get with your kid, and you would like to not lose more than you already have to.
8) Have the audacity to tell your kids what you expect of them, regardless of their location. You lose all right to tell your kids such things when there is a SM around as she is mom of the house and makes the rules for your children when you are unable to be there for any given amount of time.
9) Request your kids SM not be involved in things like school or medical decisions. Go so far as to be involved in every volunteer opportunity that you can be or to bring the cupcakes to school so that SM feels like you're only doing it to get to her, because, once again, it has nothing to do with the fact that these are your kids and you just want to do things with and for them. It's all about what you can do to get to the SM.
10) Expect dad to take care of your children together while they are with him. This is probably the one of the quickest ways to get the label of bitter or bitch from someone. Because they are a family and married couples jointly raise kids together and it doesn't matter that dad only has weekends and should have very little trouble telling a kid to go to bed or brush their teeth or spending time with them without his wife.
After you point out that dad is capable and that you expect the only other parent do the job he signed on for be prepared to be told that you don't respect him as a parent while being told that the kids wouldn't be taken care of it wasn't for the woman in the house because men are incapable and haven't learned anything about raising kids.