I've been following your thread appalled at the behaviour of your in laws.
I think some people on this thread have totally missed the point stitch. Yes, we all know that names are a contentious issue. We have all heard stories of families disapproving of relative's name choices and having a sulk or even a super duper argy bargy. Your in laws don't like your name choice - so far, so normal. A normal family might raise eyebrows behind your back. They might express their unhappiness to your faces and then shut up. They could even keep on muttering and grumbling every time the name subject arises. But in the end, a normal family knows it's only the parents' choice.
What is by no means normal is the way your in laws are trying to exert control over your dh and you by cutting comunication with you both.
In what conceivable way do they think this is rational behaviour? They risk potentially losing their relationship with their own son and precious grandson through a sulk. It's extremely manipulative and narcissitic.
FWIW we named our dcs both our surnames (like you) and my dad was strongly against us doing this because it's not traditional in his culture. (He's very elderly, very conservative). Despite his opinion, which he has told us clearly, he has never once sulked, grumbled or ever tried to undermine our decision because he's not a manipulative narcissist.
I'm afraid it sounds like your inlaws are so deeply entrenched in their patterns that it's unlikely they'll have the capacity to consider their behaviour objectively. They are not going to suddenly realise they are being unreasonable because I guess their strategies at manipulating your dh's behaviour have up to now always been successful and this then reinforces for them the feeling that they are right. I think your dh will need to spell out very clearly in absolute specifics how they need to behave if they want to retain contact. So perhaps an email with some rules along the lines of when, where, how:
Hi Mum and Dad From now on if you would like to contact us through skype it must be a friendly and respectful experience for everyone involved. Therefore you will greet whichever adult is there with ds and make friendly conversation. You will not complain, ignore or otherwise behave disrespectfully towards either myself or sphinxster. . If you cannot comply with this we will no longer be able to continue our contact. Love DH
The dh will need to be super duper tough and stick exactly to his rules - no excuses (oh but they didn't mean it) no second chances (but they love ds so much). The minute his mum starts ignoring him or his dad starts huffing and puffing he swithces off skype. For good.
Good luck little Sphinxster family. There are rocky times ahead while you all learn to live in the new way but it can be done and it's so worth doing.