Hmm, tricky one - yes, all too often the arrival of a stepmum does change the way in which a dad parents, but that isn't necessarily the stepmums "fault".
I agree, but in an immature young mind, they will see it as black and white, ie. all was fine before, SM arrives, things changes in a way I don't like, therefore it's her fault, therefore I don't like it and will show it to her.
I personally hate, really hate this 'disney dad' reference. I have never heard it except from the mouth of SMs who are not happy with the way their partner's discipline their kids. There is no right or wrong way to discipline and it is often only years later that you can decide whether the way you've disciplined your kids was best or not. As a principle, I think dads should be left to discipline their own kids as they believe is appropriate, whether it perceived as too lenient or too severe, however, I totally respect that when it is vastly different to how a SM discipline or would discipline her own kids, it is going to cause a problem.
This is exactly why I strongly believe that getting together with a man who has children should mean taking things even slower than you would otherwise. This matter is one that my OH and I discussed on our 3rd date I think, because it was extremely important we were going to be on the same wavelength on this. He previously had been in a relationship where he couldn't stand the DD's behaviour and the way she was disciplining her. It highly contributed to the end of the relationship. He needed to be sure that I was 'strict' enough and my kids well behaved. From my perspective, I needed to be clear that I would not accept him imposing his discipline to my kids, so really there was only one way forward and that was to agree in the first place! Thankfully we did, and indeed, it was part of us realising that we share similar values and principles in life which I grow to realise is as important as love to make a relationship work.
Even then it is not easy because lovely kids become grumpy teenagers and well, you have to love them deeply in the first place to cope with some of their behaviour! However, our relationship has grow so that we can communicate and reach compromises to make it work.
I don't think there is anything wrong at all with dads adapting some of their parenting style learning from a new SM, as long as this happens because they see the benefits rather than doing it for a 'quiet life' - and I have to say that I have heard a number of dads admitting that they do go along with their new partner because they can't cope with the constant grumpiness and nagging otherwise - and it is done in a such a way that kids have time to adjust to it.
As a rule, whether a parent, step-parent, teacher, I do think that kids will respond very well to any discipline as long as it comes with gratification, usually by actions/behaviour that will raise the kids' self-esteem. My kids' SM will ask them to do things they don't want to do, but she is also extremely complimentary of them, so the balance is there. My SM was much stricter (and had higher expectations) than my dad AND my mum who were much more similar in their approach to discipline. I was quite an easy child though and adjusted without problems to stricter teachers. The problem though was that my SM was only always ever critical. I don't remember seeing any long of pride or love in her eyes, always these disapproving looks and rarely a nice world except for when I was fully compliant to her demands, and then it came across to me as defiant to prove her point.
The reality is that if you don't like someone, however much you think you are hiding it, that person will feel it and respond to it. Kids are extremely perceptive, maybe because their verbal communication skills are not as developed so they pay even more attention to basic signs which as adults we are not forcibly aware of.