So far no-one has explained how the west is supposed to deal with terrorists by negotiation?

Since most of the "terrorists" that the "west" is currently "dealing" with at this time, are terrorists of our own creation, the simple answer would be to stop creating them. And to stop creating the conditions that feed the desire of others to support them. It's not Democracy most of these people have a problem with. Most of them would probably like to live in democracies themselves. What they have a problem with is imperialism (US and British imperialism), which makes it impossible for them to experience democracy or freedom because, very likely, the US and Britain are propping up totalitarian dictators in their own countries. Big, big, difference.