There's a repulsive element in large numbers of people supposedly united for a common cause. When wisdom and reason are abandoned and solidarity is adopted for its own sake, regardless of the validity of its premises, the mob becomes a spawning pool for unbridled passions and zealotry. I have tasted of such seemingly sweet fruit, which intoxicates with its illusion of certainty, seduces with its attractive facade of infallibility. The crowd encourages a natural multiplication of error, of blind belief, of desperate stupidity.
Far more good is done through individual action and commitment that doesn't depend on the security blanket offered by the chanting, gesticulating masses for its strength. Collectives have always been vulnerable to the skilled manipulations of a clever demagogue (or gang of demagogues). Gather a crowd in one location and they are at risk of succumbing to theatrics and bombastic rhetoric that fans their irrational fears, hatreds and desires. It's as if the mass of people act as conductors of overcharged emotional electricity, filling the very atmosphere with sparks that could start a conflagration.