There is no cause so right that one cannot find a fool following it.
To prove a point, one may seek out a foolish Socialist, thirteenth century Liberal, Scientologist, High Frontier advocate, Mensa member, science fiction fan, Jim Bakker acolyte, Christian, witch, or fanatical devotee of Special Interest Lib. It doesn't really reflect on the cause itself. Ad hominem argument saves time, but it's still a fallacy.
Also in Fallen Angels (Baen Books, 1992) as: "Niven's Law: No cause is so noble that it won't attract fuggheads." - Niven's Laws