“Every idea is an incitement. It offers itself for belief, and if believed it is acted on unless some other belief outweighs it or some failure of energy stifles the movement at its birth. The only difference between the expression of an opinion and an incitement is the speaker’s enthusiasm for the result.”

So the more passion behind an idea makes it more believable? Reason and facts should drive an idea forward. It was believed the sun revolved around the earth, and the earth was flat. Regardless of how emotional someone gets in that belief, the facts, reason, point to a different conclusion.

He is speaking of political expressions. We can all say we despise the government for one reason or another in a quiet debate. People have done that constantly throughout history and governments are not threatened by that. When people show too much enthusiasm (in government's eyes), they are called revolutionaries and are accused of everything from incitement to treason.

Talk, talk, talk -- we love to talk. But when the communication inspires action, that is real force. However, if 'truth' is trampled by 'passion' the mob can ethusiastically destroy the very foundation of freedom.