Older people sometimes don't "get it". Or maybe they just don't care? My dad has always been very negative towards me. I had to tell him I couldn't go on a trip with him if he was going to do his usual thing. Of course, he put all the blame on me. I repeated myself several times until he got it. He didn't admit blame, but conceded he'd be nice if I was. Maybe you could try something similar? No blame, accusing, just point out that it's not the best way to communicate.