I was riding in the jumpseat on a Friday night flight from Frankfurt to Heathrow, a flight I took about 40 times in two years.
We'd landed and were stopped, waiting for an aircraft to cross in front of us before we could get to our gate. One of the cabin crew called up the flight deck and told us that several people were standing and were refusing to sit down as they were in a hurry.
The captain spoke on the PA :
"Those of you sitting down might wonder why we've stopped. I have to apologise for delaying your journey but we are unable to move while any passengers are standing."
Polite, effective, and guaranteed to make those idiots who wouldn't sit down feel very small indeed.