This is not a bug. This is a designed feature.
Certain (sharp) items, though able to open canned goods, are items not intended for this use and will be damaged when used in this way. The only item that won't be damaged from opening them is a can opener.
Dean covered this in a devblog a long time ago. If you think the degradation rate for the bayonet is too quick then make a post in the suggestions thread of the forum. This however is not a bug.