Why does the "disable" console command not work in certain areas such as the Fighter's Stronghold?

Is there a way to fix this?

Tell us more about how you are attempting to use the command, then we might be able to provide you with some tips or solutions.

I go to console, I click on an object I want removed, I type DISABLE, then enter. This works in most places...

Some mods can be written to override console commands or game functions. This protects the mod from possibly corrupting the game. For example, the mod "The Elder Council" disables fast-travel in certain quests.

So if a mod program is running within Oblivion, and disable won't remove an object, then that means either the mod has blocked that command, or the object you're trying to get rid of is hard-coded into the game. The charred corpse is a hard-coded object in Oblivion (no Form ID for it).

So there is no way to remove NPCs from the Fighter's Stronghold?

Indeed; in addition, Fighter's Stronghold is an official mod, so that may cause this, too.