That would be just shitty for kids. Your parents are from A and B, but live in C. A and B are hard to enter without citizenship and impossible to live/work in long term without it. If you limit multiple citizenships, you basically kick the child and limit their family access without any reason in that situation.

In your scenario, a C-only citizenship child with an A parent and a B parent is no worse off than say his peers who have C-only citizenship, and whose parents have C-only citizenship, too.

It's not like any of those C-only peers could easily visit or move to A or B, either, based on how you've described their policies.

If anyone is worse off in that scenario, it would be the C-only children with C-only parents. Those families are pretty much stuck dealing only with country C, no matter what. The multi-citizenship family, on the other hand, could potentially benefit from the ability of a parent returning to A or B for a period of time, for example.

You seem to be mistakenly portraying the family with more options and flexibility as "victims", when in practice they're actually much better off than others are.

It depends how you look at it. Sure, policies would be the same. But if you think about people, those kids may have minimal chances of seeing their extended family for years.

Many countries don't allow for double citizenship, but sometimes they have to make exceptions because some countries don't allow you to renounce to your nationality

You can't get rid of a greek citizenship,its impossible. I think thats how it should be.

The games with revoking citizenship of Snowden, etc. ate absurd and should not be allowed. Even if the person is a criminal, he must server punishment defined in law. He is still 'your' American/greek/ whatever criminal