“Fanatic—a person filled with excessive and often misguided enthusiasm for something.” (Concise Oxford Dictionary)
Fanatics killed Jesus and Stephen. Though once a fanatic, when Paul became a Christian he too was hounded by the fanatics he was once like.
Fanaticism seems to control the day in our current culture.
I found the following article enlightening and helpful. I hope you do as well.
“Fanaticism has one respectable feature, that it is sincere. The fanatic believes what he asserts to be true, and he is earnest and zealous in the maintenance and propagation of his belief. But when we have said thus much we have said all that can be said in his favor. In fanaticism there is a culpable neglect of the reason which God has given to man to be his guide. The fanatic shuts his eyes and closes his ears, and rushes on his way with no more reflection or discrimination than a wild bull in its fury. Fanaticism, too, has a fatal tendency to deaden all moral considerations and to blunt a man’s perceptions of right and wrong. It is in vain to look for justice, or fairness, or truth, or mercy, from a fanatic. There is no violence of which he is not capable if he thinks his faith is in danger, no wiles and baseness to which he will not stoop if he thinks it necessary for the defense of his cause. Murder, perjury, bribery, subornation of witnesses, and defamation of opponents by lies and slander, have constantly been the weapons by which fanaticism of various kinds has ever defended itself. The end justified the means.” (Pulpit Commentary on Acts, vol. 18 p. 196)