A person's ideology is different than the ideas contained in a specific religion or philosophy. To say that Islam is evil because it helps to shapes a terrorist's ideology and action is bogus because it also helps to shape a peaceful person's ideology and actions.
Well, that sounds like you're saying that a person's philosophies never shape his actions. I don't mean to misquote you and please correct me if I am, but that's how I'm reading your statement.
I disagree with that. When a parent lets their child die painfully because they tried to pray away the meningitis instead of taking him to the doctor, Christianity is to blame, even though the vast majority of Christians would never consider doing something like that. Their interpretation of Christian beliefs is what led to their child's death and absent that Christian belief, the child would have been fine. The ideas in the Christian philosophy which formed their belief system are what led to the result.
If a person becomes a vegan and his interpretation of how a vegan is supposed to eat causes him to lose 50 pounds of fat and drop his cholesterol levels, then veganism is responsible for the resulting health benefits, regardless of whether or not most other vegans would agree with his interpretations.
It's the same with actions stemming from Islamic beliefs. If a terrorist shoots up a crowd of civilians because his interpretation of Islamic faith is that all non-Muslims should be enslaved or executed under a Global Islamic Caliphate, then it is Islamic philosophy which led to that result, regardless of whether or not the accountant who lives down the road from him has an Islamic philosophy that he should just be a generally decent person who respects others' beliefs. Absent his belief in Islam, nobody would have died because that belief was the motivating factor in his behavior.