THE MARK OF THE BEAST, JUST A SYMBOL OR REAL ALLEGIANCE?

When I was in Bible College in Montreal Canada, there was an instructor who argued that having the mark of the beast wasn’t an issue as long as a believer did not believe in it and didn’t put his heart into it. I was in total shock but my fellow students seemed to go along with it, I don’t know if there were silent disagreements among them, but I felt that if there was ever such a thing as heresy, this was it. I would like to know how you would have honestly reacted to such comment from a Bible College instructor? Do you think that such Bible College equips students for effective ministry?