Most FAs would tell that the passenger is having a meal and everyone I have seen always put their seats up. I would also ask them and no one has ever refused or said anything as they know the situation during meal times. On the other hand yes I would wish they would not recline their seats but it is their right to do so. Just as it is my right to recline mine. I never had anyone complain about it apart from one flight a few years back I think it was a continental flight from Miami to New York. A kid kept banging away at my seat and I had to tell off his father to stop it.
This is the same scenario where passengers refuse to draw the window shades down. I think it is very selfish of them to refuse to do so as many a time the sun is in the eye of some other passenger.