When I use Vision Charm to phrase out Dreadnought when it just comes into play, do I need to sac my own creatures?

Many members here are quite sure that I don't need to sacrifice (Look at the Dreadnought Affinity Thread):

Ability goes on the stack, you vision charm the nought, charm resolves and nought phases, you chose the "sac dreadnought" option when it's ability resolves, and since dreadnought is no longer 'in play' you don't have to sacrifice anything.

...

When Phyrexian Dreadnought comes into play, sacrifice it unless you sacrifice any number of creatures with total power 12 or greater.

The 'default' option is to sacrifice the Dreadnought. You can't be forced to sacrifice 12 power worth of creatures.
But only that 'Virtual Judge' on StarCityGames.com makes me feel unconfident about this issue:
Q: If I play Phyrexian Dreadnought and then, while the triggered ability is on the stack, play Vision Charm, making Phyrexian Dreadnought phase out, what would happen with the triggered ability?

A: It will still resolve, and you will have to sacrifice creatures with a combined power of 12 or greater if you have them, or at least sacrifice as much as possible. The fact that the Dreadnought is not in play does not matter, other than the fact that you will not, and cannot, sacrifice the Dreadnought, even if you cannot sacrifice enough creatures.
Is there a part of the rules or an official statement I can refer to if I have to argue with a player or a judge?

I would be happy if that could be clarified.

Thanks in advance

Odabella