The fire did this, not the meat. Bitter, acrid flavor comes from smoke that never finished burning — a thick white or gray plume loaded with tar and unburned wood compounds — and once that smoke settles onto a moist surface for hours, trimming away the worst of the bark is close to the only recovery you get.
Why white smoke tastes bitter and blue smoke doesn't
Wood smoke is never one thing. A fire burning hot with enough oxygen breaks most of the volatile compounds in wood — the phenols, guaiacol, and other flavor molecules — down further before they leave the firebox, and what escapes is a thin, almost see-through wisp with a faint blue-gray tint. That tint isn't decoration. The particles in it are small enough, sub-micron, that they scatter blue light more than red — the same effect that makes distant mountains look hazy blue.
Starve that same fire of oxygen and combustion stops halfway. Larger droplets of unburned tar, creosote, and concentrated phenolic acids ride out in a thick white or gray plume instead, particles big enough to scatter every wavelength evenly, which is why the smoke reads as flatly white rather than tinted. Those heavier droplets are also what land on the meat in bulk. The bitterness is that tar, cooked directly into the surface.
What actually starves a fire of oxygen
A firebox chokes for a small number of predictable reasons, and each one happened a few minutes before the smoke turned white. A big, cold log added all at once smothers the coals underneath it instead of catching cleanly. Closing the intake vent down to control temperature cuts off the same oxygen the fire needs to burn clean, not just the oxygen that makes it hot. Wet or unseasoned wood spends its first several minutes boiling off water instead of combusting. An ash bed built up under the coals blocks air from reaching them at all.
The fix isn't more wood. It's smaller, more frequent additions of dry, well-seasoned wood or charcoal onto a fire that already has flame or hot coals to catch onto, with the intake open enough to keep it actively burning instead of glowing and cooling.
Whether this batch is worth saving
Not much of it. The bitter compounds haven't just landed on the surface — they've worked into the proteins and fat of the bark over hours of exposure, the same way flavor compounds from good smoke do. Trimming away the outermost layer removes the worst of it, since the interior meat was never in direct contact with the smoke. What you can't do is rinse, marinate, or sauce your way out of it. Those cover the taste for a bite or two, and then it's back.