It is Allah's word just as it is in the Koran. We are also not allowed to translate it. It is unimportant whether what it says is well received or not. We are not allowed to question even a single word.
All people should disclose whether they submit to Allah or not. Those who are against us are our enemies and must be fought. That includes people who call themselves Muslims but who don't lead their lives as such - people who drink, who don't pray, who don't fast, who have constantly changing partners and who are unable to recite the Koran.
It is not true that only those people come to Islamic State who have experienced no success in life. Among them are many people who have university degrees, people who were well-established. But they all see the inequities that we Muslims have long experienced and want to fight against them.
Christians and Jews go after those who have access to raw materials but who prevent access to them. Oil is the best example. The US and its allies are constantly intervening in countries where they don't belong only to defend their prosperity. We aren't fighting because we are greedy and selfish, rather we are fighting for values and morals.