People do have mentalities, but religions/ideologies are "channeling" these mentalities. Bigger ideologies are/were never meant to direct just one type of person/mentality, but they coordinate what place a person with a specific mentality has in society. And Islam clearly has a "forgiving" or even encouraging stance on violent acts/mentalities.

That doesn't mean that it's the peaceful people that are encouraged to act violently, their role in the islamic society is to build a solid foundation in the society, while it's the aggressive people that have the role of crushing dissent and suppress rivaling ideologies. The biggest challenge is to balance accepted aggression and internal peace, so that peaceful people don't turn away from the social model. It's clear that Islam is doing a good job with that if you observe the polls on justified violence and support for less demonized terror groups, like Hamas, Taliban and especially Syrian "rebels". Islam seems to have a big disposition towards conspiracy theories, that would reinforce the inherent victim complex that is promoted in the quran and throughout islamic history.

To be fair, most societies have this way of channeling mentalities, some more extreme than others. So Islam might not be a problem in itself, but it definitly is a problem in context with non-islamic societies. And I say Islam as a whole, since crucial parts are defined in absoluts. An immutable word of god and an infailable person draw a rigid line on where dissent begins and violence is justified. Every brand of Islam that doesn't think that the quran is immutable or at least refuses to assume that the life of the person described in the sunna is examplary, has a chance of becoming a problem on the level as any other ideology.