This survey, being from November of 2006, does not include "NONE OF THE ABOVE." as an option.
Snape's twisted mind was loyal to something, but it ain't on this list.

And while we're on the subject of "loyalty," any loyalty to Dumbledore is beside the point.
Taking down Voldemort was the main issue.
If an enemy of an enemy is a friend, then yes, Snape was Dumbledore's friend.
Personally, I prefer that my friendships be... oh, I don't know... something more.

People were fighting and dying for what they believed to be a worthy cause, and
Dumbledore just happened to be the leader.
You'd have to be a fool to fight like that just because some old man asked you to.