The Rogue Tomato said:
I think it's extremely rude unless you are asked (which typically doesn't happen during a sermon but I've seen it before). I'm not a pastor but I would ask him to discuss any grievances with me in private after the sermon and then tell the individual that all things are to be done decently and in order (1 Cor. 14:40). Also I was reminded about a certain incident when I read this thread.
http://tahoecommunitychurch.org/wordpress/?p=1812
"Finally, I thought it was over, but she walked up to me where I was seated on the front row, and began “prophesying”. She said, “Young man spit your gum out and face me”. I got up (probably should have just walked out), and she began telling me how I thought I had come as a peacemaker, but was really there because God had used the hecklers to get me to her tent because He had something to give me through her. Then she went on and on saying all kinds of stuff, including that I said or thought that her ministry was a work of God, and that she was doing good and trying to help people. That was a lie. I never led her to believe any such thing. At that point I felt I needed to make it clear that I didn’t agree with her message or ministry, and that’s what I tried to do. Sadly I think it appears more as though some guy got in a prayer line or requested prayer and then seized on the opportunity – which isn’t true."