Here's a link to an interesting article regarding the laws governing the military trials of terror suspects and perpetrators.
http://www.aclu.org/natsec/emergpowers/14373leg20011129.html
This is an excerpt from the article linked above which I believe may shed some light on your question of "why people support the terrorists?"
The breadth of the President's order raises serious constitutional concerns. It permits the United States criminal justice system to be swept aside merely on the President's finding that he has "reason to believe" that a non-citizen may be involved in terrorism. It makes no difference whether those charged are captured abroad on the field of battle or at home by federal or state police. It makes no difference whether the individual is a visitor or a long-term legal resident. Finally while the order applies in terms only to non-citizens, the precedents on which the President relies make no such distinction, permitting the order to be extended to cover United States citizens at the stroke of a pen.
The basic, fundamental rights guaranteed in United States courts and in ordinary courts-martial will not necessarily be afforded the defendants. The order purports to prevent review by any civilian court - including the Supreme Court of the United States - to ensure that even those rights ostensibly granted in the military proceeding are not violated. The rules and regulations that govern the tribunals are still being formulated. But, at the Pentagon's discretion, trials can be conducted in secret, and evidence can be introduced without the defendant being able to confront it. Only two thirds of the military officers on the tribunal's jury need find a defendant guilty, and the order provides for no meaningful appeal, even in cases involving the death penalty. Other basic rights remain unprotected. These rights seek to ensure that the government gets it right, punishing the guilty and permitting the innocent to be cleared.
In lieu of these comments you should see how these provisions could seem threatening to any citizens rights and freedoms. Obviously these sanctions on the regular justice system were not imposed to detain your average citizen at the slightest whim of the president's fancy, but rather for the purpose of detaining legitimate terror suspects.
The real issue behind support of these suspects is that anyone who's bickering about these cases is obviously left of centre (at least...most likely far to the left). That's why you have statements coming from them like "He was only a child when he threw the grenade :crybaby:". Oh well...so what, give him another 5 years then. Anyone that thinks that living in Afghanistan he would have shifted to a more lenient stance on Western policy is out of their mind...it would have been the complete opposite. That's why we're fighting there for God sake!!
These people are terrified of anything that may infringes upon their rights and freedoms (even if it's intent is to bolster national security)...They are the types of people who like to organize protests and parades in support of whatever the hot button issue is at the time, be it the rain forest, gay rights, abortion or the rights of potential terror suspects. They're afraid that they'll have their rights to protest/clamour about their little pet projects smashed to pieces by "Big Brother". The bottom line here really is that these people don't live in a little place I like to call REALITY...and I stop right there before I fly off the handle and go on an angry rant.
hope this gives you some insight