If you aren't wearing muffs indoors or out to shoot, then you WILL damage your hearing, whether .22 LR or .44 magnum.
(Ask me how I know)
You may not notice it now, but you will when you get older. Guaranteed.
But, a magnum revolver isn't any problem with hearing protection.
Also, with proper hearing protection every gun is a quiet gun.
I think he's referring to a self-defense shooting indoors rather than indoor range practice shooting.
