I don't get that either.
V basically tried to overthrow government.
Vivec stuck his metaphorical and metaphysical pee-pee into a god's mouth....
I don't see the similarities....
I like how you compare a character to a single action of another character...
I'm thinking Astion thought the same thing I did. Both have the name V, and V from V for Vendetta really was a sort of warrior-poet, both vastly intelligent and a skilled fighter, spouting quotes from the classics wherever he went. V was also more than a little slightly unhinged too.
But if the name V doesn't come from V for Vendetta, why was it chosen? Vehk is the only member of the Tribunal that doesn't have a complete name.