Magworth, your guide tried to be sensible but he has deprived you of a fun evening. There is no danger in going to Pigalle if there is a group of you, and so long as you stick to main streets, main places (Moulin Rouge), etc.
You can also make it as part of a longer visit in that part of Paris, going from there up to the Sacre Coeur and then Place du Tertre, where all the amateurs painters are. It is very tourist oriented nowadays, but still worth seeing to my mind. Avoid having a drink in any of the bars - they are much too pricy.
I remember taking my English cousins there one night and the barman in one cafe tried to charge us exhorbitant prices; I gave him a piece of my man in very well chosen Paris slang words and he soon reduced the bill !