Begin this section by understanding it is what he scratches not that he scratches that is the problem. The three most common reasons for destructive scratching are nail maintenance, marking territory, and stress release. Nail maintenance is pretty much a side benefit to most scratching. From the look on cat's faces when they scratch, we suspect it is pleasurable for them to sink their claws in and pull. Probably gives a wonderful stretch to all the retractor muscles in the paw.
Scratching cleans the nails up, removing the scaling outer shell.
It also sharpens the claws. You can greatly limit the damage done by a scratching cat by keeping his nails trimmed short. Only do this if your cat is an exclusively indoor animal. Marking territory is the usual motivation for this behavior. As all cats have a number of zones they are aware of, cats in general, males in particular, tend these territories carefully.