If you don't want to be thrown into Gehenna, read what your own faithful evil slave & Christ say:
cj chap. 3 p. 110 Chapter 3 - "Jesus Christ said: “Whoever says, ‘You despicable fool!’ (apostate) will be liable to the fiery Gehenna.” (Matt. 5:22) The person who wrongly condemned his brother as a “despicable fool,” (apostate) that is, as being morally worthless, would be in great danger of such a serious consequence. This is because he would be viewing his brother as deserving the judgment of Gehenna, or hoping that his brother would suffer that judgment. In his heart he would be desiring this for his brother and, therefore, would be putting himself in line for the punishment he wished for the one whom he was calling a “despicable fool.” (apostate)
w78 4/15 p. 22 - "Jesus then went a step farther, saying: “Whoever says, ‘You despicable fool!’ (apostate) will be liable to the fiery Gehenna.” (Matt. 5:22c) The Greek word rendered “you despicable fool” is mōré. A similar-sounding Hebrew term (moreh) means “rebellious,” “mutinous”...mōré designates one as morally worthless, an apostate and rebel against God."
Heresy is any belief or theory that is strongly at variance with established beliefs or customs, particularly the accepted beliefs/religious law of a religious organization. (A heretic disagrees with one or more teachings of the religious hierarchy)
Apostasy is the term used to describe the renunciation and criticism of, or opposition to, a person's former religion. (An apostate completely abandons their religion and openly denounces it)