He may feel threatened by his old age and/or any medical conditions he has. Threat perception can change people in strange ways, and sometimes make them defensive with the need to prove themselves, and/or establish dominance.
Has anyone had a "come to reality" talk with him? Perhaps he doesn't realize how offensive he is.
You don't mention Dementia but if sudden he could have a Urinary Tract Infection (UTI). This will change his personality somewhat. He may be in early stages of Dementia. Best thing is to get him to the Dr. for a complete evaluation, labs included. Low Potassium will cause problems. Dehydration and diabetes. Thyroid.
Has anyone had a "come to reality" talk with him? Perhaps he doesn't realize how offensive he is.