The sermon. in some shuls. “
And although that was a cute answer, I have a serious response. For kovod haRav alone, it is really improper to walk out just as he begins his drosha. Even if and when it is boring. That is a D’var TORAH he is giving over. Just not nice to walk out. We have to do a lot of things in life that we might not care too much to do. Having and acting with simple derech eretz may be a tircha for some people, but they are the ones most in need of it. And if the sermon is really bad, remember that lifum tz’arah agrah. You get extra brownie points for staying and listening.