The doors segments have entities (the actual swinging or sliding door part) which can be adjusted in the properties of the editor. Set the door entity strength to a lower number and it can be destroyed. Depending on what you want to be used to destroy it, you'll have to play with the strength to get it right.
Don't forget, Destroy in FPSC means disappear, not explode or break apart. By using the crumble.fpi script I think it is, you can get a little better effect, but the door still just disappears.
Best.
I'm sorry, my answers are limited. You must ask the right question.