I've met people who, despite being very good, godly, loving people, nevertheless think that the United States deserved 9/11 and refuse to blame the terrorists. It wasn't their fault, they were driven to it by US foreign policy or something similar. My response to this is threefold:
1. This first one is commonly stated, so please forgive the repetition: but how is this any different than blaming a rape victim? Any example you can give me as to how the terrorists were driven to do what they did, I can say something similar to place the blame squarely on the shoulders of the woman who is raped. She was wearing a short skirt, she invited the guy up to her room, she was flirting, she was leading him on, etc., and by so doing, she inflamed the rapist's sex drive beyond his ability to control it. If you can't condemn terrorists, I don't see how you can condemn the rapist. But obviously this is insane: the terrorists, not their victims, are responsible for their actions, just as the rapist is responsible for the rape.
2. If the terrorists were driven to their actions by the US, and are therefore not responsible for them, why wouldn't this apply to the US as well? Why couldn't we just say, "The US was driven to their actions by the actions of other countries," or something? If the terrorists can't be blamed for their actions, I don't see how you can blame the people who allegedly drove them to their actions either; since these people were also driven to their actions by a third party, who was driven to his actions by a fourth, etc, ad infinitum. The only way to avoid this absurdity in which everything everyone does is always and only a reaction to something else is to stop it before it starts. And this entails that the terrorists, not US policy, are responsible for their acts of terrorism.
3. I don't care what the terrorists' excuse is for their atrocities. There is never an excuse for terrorism. Period. Once you've committed an act of terrorism in order to promote a particular cause, for that very reason I will no longer pay any attention to your cause. The only thing I will pay attention to is forcibly stopping you from committing any more such atrocities. I refuse to reward bad behavior in general, and especially so when it comes to horrific acts of depravity.
This is not just an ethical position -- a refusal to accommodate evil -- but a practical one as well. If we allow the terrorist to have any positive response to his atrocities, this will simply encourage more atrocities. "We want more money for our country's infrastructure." BOOM. "We want a chicken in every pot and a car in every garage." BOOM. "We want you to imprison anyone who says things we don't like." BOOM. Again, the only way to avoid this is to never allow it in the first place. Even if your cause is worthy, as soon as you use terrorism to promote it, it immediately moves off my list of concerns.