Backing Down to Cowards?
It is patently obvious that many terrorists aren't cowards - they perform suicide bombings, sacrificing their lives for their cause. This doesn't justify their ends or means, but it's hard to say that someone like that isn't courageous, unless "courageous" just becomes another propaganda term that ascribes only to us.
If they're not, they're as cowardly as those who perform pinpoint bombing campaigns that kill 20,000-100,000 lives, and the country of those cowards that says that 1000+ casualties is far too high and a quagmire like Vietnam, and that those troops should be protected even better than they are.
Arguing that giving into terrorism encourages it assumes that people are simple incentive/disincentive processors like Skinner's pigeons. It's a mechanistic outlook that ignores the true sources and the passion behind terrorism. Mind you, this is an empirical argument. Here's an article from a conservative magazine that disproves it. http://amconmag.com/2005_07_18/article.html
In any respect, saying that "giving into" terrorism by adopting the policies they propose is a massive irrelevancy if those demands were the right thing to do. One would do the right thing even if terrorists provided the impetus for it to be done. So when Middle Eastern terrorists ask for economic development or point to American occupation, they're right.
No one on the Left I've seen JUST proposes that we attempt negotiations; they say that real law enforcement should be done to bring people to justice. That provides all the disincentives one needs. Rather than saying, "Instead of giving into terrorists, we will bomb hundreds of thousands of innocents to death.", which doesn't stop terrorists (because that's not the intent) nor does it make one seem especially magnanimous, leftists propose saying "We will bring any criminals, including our own, to justice. And any demands or proposals made by these criminals that are legitimate we will institute in the hope that that reduces their base of support as well as for independent reasons.", which seems far more effective and just.
Does one not negotiate in a war even if the other side bombed civilians? This is an especially important thing to note if your side did it too. I should not have to belabor the fact that the US war on terror is a terrorist war.