I think that negotiating with terrorists can be justified in some circumstances. It really depends on if lives are at stake and what the terrorists want. If what we give the terrorists will easily allow them to kill many more people then it probably isn't worth it. If not then it is definitely worth it.
If logical negotiating is possible then it should be done. Negotiating is a good thing and shows maturity and respect for others. Being willing to talk shows respect and intelligence to others. You don't have to give in to demands or appear weak, but being unwilling to even talk comes off as thinking you are better than others, and is almost a form of being a bully in itself.
If there is a want to negotiate with terrorists, whether it is money or aid or some other way, it is probably better than going to war. Anything to keep the peace is good. And, if you were to attack instead of negotiate, you will still never end terrorism as we know it.
I do not believe negotiating with terrorists can ever be justified. Terrorists do not make demands with the understanding that they will bargain down. History shows us that if demands are not met, terrorists have no compunctions about killing any number of people. You can not negotiate with someone who has no conscience.
No, I do not believe negotiating with terrorists is justified in some circumstances, because it will encourage other terrorists to take drastic actions. It the terrorists know that we are willing to make concessions, they are willing to take even more aggressive actions because they have been successful in making us willing to change.