This is a pretty good
Quillette article on islam and terrorism.
Apologists claim that whatever violence Muhammad employed was legitimate self-defense. An inter-tribal revenge murder was supposed to have constituted a violation of the truce with the Meccans, justifying the conquest of Mecca. Two years earlier, the Jewish community living at the oasis of Khaibar allegedly entered into an alliance with Muhammad’s enemies, providing a pretext for the Muslims to attack them. After their defeat, the Khaibarites were made to pay fifty percent of their produce in tribute to their Muslim masters for the privilege of living on the oasis. Umar, the second caliph, nevertheless expelled them several years later on the grounds that they were causing mischief.
It would be interesting to hear the Meccan or Khaibarite side of the story. Since we don’t have their accounts, I will note on their behalf that it is a strange set of circumstances in which self-defense necessitates conquering a city, destroying religious artifacts, declaring your religion to be the only one allowed, and extracting exorbitant amounts of tribute from weaker populations. The fact that Muhammad’s immediate successors conquered huge swathes of territory does nothing to quell my suspicions that his actions may not have been defensive manoeuvers.
You might think: why should that matter? That was a long time ago! It matters because Muhammad’s life is normative for Muslims. The shahada, or Muslim profession of faith, is “There is no God but God and Muhammad is His messenger.” Muhammad is the messenger not only because it is through him that the Qur’an was revealed, but also because his life is an example. That is why tremendous efforts were invested in collecting and sorting the Hadiths, reports about Muhammad’s life, in the Sunni tradition. If Muhammad was intolerant and aggressive, then there are good grounds for saying that you, as a Muslim, should be as well.
That's the biggest problem with islam. Old Mo was a warlord, a conqueror, someone who made his followers kill his critics, a rapist and a pedophile. That was par on the course for tribal leaders of his times and I don't think he was much worse than other Arab raiders or even Christian kings and nobles.
However Mo is simply not a good role model for today's world. Most of the things he did are considered crimes and morally disgusting in a modern society. Even most modern muslims consider those things wrong...when it's
NOT Mohammed doing them. Tell most muslims a story about a Chinese warlord who killed, pillaged, forced women to marry him and impose insanely high taxes on the people he conquered and the vast majority of them would agree that the Chinese warlord was vile and deserved punishment.
But when it comes to Mohammed it's all OK Because He Did It. So there are lots of justifications, rationalizations, double standards, etc. to whitewash Mohammed's unethical actions.
Until muslims learn to accept this, and move on from the letter of the texts and the justifications into a candid admission that the values of Mohammed's age are no longer valid and things have changed there can never be any sort of improvement of muslim-majority countries or muslim minority in any other countries.
Only a thorough secularization and reducing the power of islamic institutions (islamic education, islamic law, mosques, "cultural centers") can put an end to islamic violence and other issues.