In the right hands, experienced hands, all power tools are perfectly fine. I am quite experienced using an angle grinder to rough shape volutes,custom transition parts, goose necks, etc on stair rails. I could apply that experience to gun building if I chose and do not see anything wrong with some one choosing to do so.
My biggest complaint and the main reason I choose not to do so, is the inordinate amount of sawdust that such methods generate.
I know of three different builders that that use an angle grinder with 18 grit discs to shape their stocks. All three take it too far , they leave flat spots and wavy horizontal highlights. Really what is the rush?