Necro Gardna Vs. Cyber Twin Dragon

So i was just in a duel with someone, and i just needed one last attack to win, and my twin dragon hadn't attacked once yet.
So naturally i attack, and he removes Necro Gardna from the game to negate the attack. Fair enough, so i attack with Cyber Twin Dragons second attack, but then he starts babbling about how Necro Gardna stops Twin Dragon all together.
Now usually this wouldnt bother me, but the fact he was using a Mill deck and i had no cards in my deck, i didnt have much choice but the argue this out.
And he even started saying hwo its the ruling. Yet funny thing is, every where i look (whether Yugioh Wikia, Pojo or anywhere else) they all say the same, it negates 1 attack, not the monsters twin attack effect, just a single attack.
In the end i just had to quit the duel, he wasn't gonna back down, and neither was i. But in the end, i just had to because i was growing frustrated.
So can anyone tell me which one of us was right?

You were right.

http://yugioh.wikia.com/wiki/Card_Rulings:Magic_Cylinder

* Monsters that may attack twice during the Battle Phase, such as "Hayabusa Knight", that have their first attack negated by the effect of "Magic Cylinder" may still make a second attack.

It's an old, old ruling, that even if labeled as "unnofficial" is still valid because it's not contradictory. It's just the kind of stuff that shouldn't need to be said, as that's how the game mechanics work.

Alright i thought as much, theres just no arguing with some people it seems.
But thanks, i'll keep that as future reference.