I suppose fundamentalist cultists gravitate toward the view that the world is evil and death is sublime because their personal lives are so unhappy and unsuccessful.
Hindu yogis and medieval Christian monks torturing their bodies, Buddhist monks and Branch Davidians self-immolating, Islamists blowing up themselves and everyone else, these folks all use the same basic rationale for their behaviour. You have to hand it to the Jihadis, though, they seem to have taken this extreme ignorance to a new low.
Yes, but comparing the iSLAMothugs to Christians, Buddhists and others is not quite fair. For only the iSLAMists believe you get an automatic ticket to heaven for murdering innocent women and children.
As to torturing the body and self immolation: the Catholic church teaches that self mutilation is a mortal sin. However mortification of the body is a means toward gaining self control. Many religions and even some non religious people fast or lift weights or run or engage in various disciplines of rational self deprivation in order to subjugate the desires to the will rather than being ruled by base animal desires. There is nothing wrong with this. It is better for everyone concerned when a man is in control of himself and his desires. Don't you think?