No, not necessary. HOWEVER, forgetting all about suppressing flash or reducing flip with a brake, etc. - to my way of thinking, the MAIN / best reason for a muzzle device on a rifle (and the reason I like them even on hunting turnbolts - well, *especially* on hunting turnbolts) is to keep mud / snow out of the bore itself, when you stick your rifle's muzzle in same accidentally, which happens often to me ... a basic "A2 style" flash hider or just anything with holes in it that traps the mud before it pushes all the way into the bore, but can be blown out through the holes on the sides when you fire preventing a serious failure / damage is a good thing. This is a good reason for having them on any rifle, including "fighting rifles". Should we do that - consolidate all the acronyms (EBR, HDR, MSR, CQBR, WROL/SHTF, PDW, etc) into just one handy phrase of "fighting rifles"? Or is "MSR" better? Which one, MSRs or fighting rifles as the better all-purpose phrase? I guess MSR might be more palatable to the blissninnies.
Oh, and don't turn anything in a lathe - just order a $7 thread protector from Amazon and put it on. Attach it with red or black loctite or similar if you never want it to come off again, or better yet, with blue loctite in case you want to sell it later to someone in a freer state.
That would be better than your 2nd best option of just cutting and recrowning where the threads begin (assuming the barrel is still at least 16").
3rd best option would be turning the threads off - would not be aesthetically pleasing.