I think when we start adding "moral" implications to the type of fly/bait/lure we throw at the fish, we add to the (sometimes real) myth of the snobby fly fisherman. If it's legal and you like it, and it catches fish - who cares? Those things will catch trout. So will crappie jigs and Rapala's ( single hook regs in most places, so watch it if you try that). So will crickets and worms and "flies" made of the filter of a found cigarette butt! (don't ask.)
As long as you're fishing within the law, I don't see the need to worry about any other moral issues. It's fly fishing. It's supposed to be fun. Or catch you dinner. Or both.