Removing them with heat will destroy a lot of the paint, so be prepared for a repaint. But you're going to need to repaint anyway, to get rid of all the nasty brass splatter whoever brazed those on left for you. I've probably removed hundreds of those, when Trek's marketing department decided to switch from over-the-shell to under-the-shell cable routing. Air-propane heat won't cut it; you'll need oxypropane or oxyacetylene to get things hot enough. Keep the heat on the shell until the braze melts, knock the piece off, then brush with a wire brush to get rid of the excess brazing material. If you do it well, a little sandpaper is all that is needed to smooth things out for paint.