Hamas - A terrorist group beyond a shadow of doubt, while also a political opponent. How and why?

Yahoo News, AP ^ | 11/14/05 | ANNE GEARAN, AP Diplomatic Writer

[sordidmesh]

...The chief U.S. diplomat also had encouraging words for Palestinian President Mahmoud Abbas, but added an indirect warning that he must do more to disarm and counter the militant group Hamas. The United States lists Hamas as a terrorist organization, but the group has recently developed a strong political wing that is a formidable opponent for Abbas...

..."Dismantling the infrastructure of terrorism is essential because in the final analysis no democratic government can tolerate armed parties with [b]one foot in the realm of politics and one foot in the camp of terrorism[/b]," Rice said at Sunday's symposium...

[sordidmesh]

Can someone explain why Hamas should be preserved like this? Is this not unlike the Taliban's inclusion in Afghanistan's new goverment? Was it not the Taliban and it's leader Mullah Mohammed Omar and his association with bin Laden that we the U.S. were fighting in 2003 and continue to battle with to this day? I know these are complicated to answer but I figured to give it try anyway. These dualities make no sense to me.