I am, I must admit, a bit of a fan of 'bean dip'. I have trouble being direct and firm, so I often come out with these perky offerings to distract people and change the subject. It usually works, but what do you do when the offender just keeps on going back to it? There's only so many times you can change the subject.
For instance: my mother at a family Christmas. She was having (admittedly quite bad) problems with some people she knew. But at Christmas dinner (at my cousin's) one year, she just wouldn't shut up about it. One by one my relatives fell silent while she ranted on and on and on. After about ten minutes, I jumped in asked about one of my cousin's (lovely) desserts and everyone leaped on the subject like seagulls on a chip. I was really proud of myself, actually, seeing all those relieved faces and hearing everyone sound appropriately cheery again.
But after a few minutes, my mother couldn't handle it any longer, and she started AGAIN, in a REALLY loud voice. This time she shot me a glare - don't interrupt me! - and kept talking loudly and quickly so nobody could get a word in. This time everyone just went silent and let her finish ranting. It took about twenty minutes with everyone dead quiet and looking at their plates.
At this point, would it have been appropriate for me (I was about 24 at the time) to be blunt and say 'That's enough about that subject, please, its' Christmas!' I'd tried polite, and she'd not taken the hint, so would it then be OK for me to be, well, not polite?