Terrorists are not interested in working within the current system. If the current system is corrupt, it's hard to fault them. If it's "democratic" (in the sense of managing collective goods while protecting individual and minority rights), then they are bullies.
The sad part is that many bullies (corrupt politicians, generals, bankers, et al.) are happy to sacrifice civilization, ecosystems and fellow humans for their power and vanity. If there is a Nobel Prize for peace, then there should surely be a list of Despicable Humans unworthy of our species.
How is it possible that they stay in power (Mao, Stalin, Mugabe) and/or receive support (Hitler, Putin)? First, the greed of those who receive part of the spoils for suppressing the minority. Second, the ignorance* of those who believe that their (in-)group is better or luckier than the (out-)group. Third, few can resist a State lacking checks on abuse of power.
Bottom Line: The march towards civilization (the freedom to develop to one's potential and enjoy the harvest of one's efforts) will be hindered by those who would suppress and exploit others. The only path for advance lies with our recognition of mutual dependence, respect for individual rights, and willingness to put aside personal goals when they conflict with the common good.
* The Saudis have crushed non-religious thought in their kingdom and paid for its displacement (via madrassas, or religious schools) in other countries. Now Pakistan is facing a collapse of science and "free thinking" bloggers (!) are being murdered in Bangladesh.