So I have an issue with a Split Open Iron Gate. I've tried to destroy it but the gate is not actually gone. I can still pass through the bars but they appear closed. What do I do to fix this?

Have you tried to relog? Usually if something like this happens, its because of syncing issues between client and server. (BTW, even singleplayer opens up a server thread on your localhost). Usually things like this can be fixed by just relogging. Hope it helped :D

How was the gate placed, and by which means did you destroy it ?

Its something that also happens with MCEdit when an area is deleted, the gates remain unless you also delete entities in a second pass. Also, with ingame building tools, such as Build Helper, things like deletion wands just cannot delete them.

Keep in mind gates are entities and have to be "killed" like any other mob, so most building tools won't effect them.

Closing as said gates are entities and thus have to be removed as such