Of course it's unnecessary; you may note that I called it a cavil, and a cavil is always unnecessary, which is part of what makes it a cavil. But it's to the point and sort of funny, which is why I left it in.
As for the rest, of course it's rude to be "playing with your phone" during dinner, and while it's sometimes necessary to initiate or answer some communication, to leave the table before doing so is only polite. But rudeness in response to rudeness is rudeness nonetheless, and justified only in the face of extreme provocation; such a minor impoliteness as the one we're discussing is far more pleasantly and effectively dissuaded by a polite response than a rude one -- something which, it seems to me, "I will disallow anyone..." evinces a certain failure to grasp.
As for the rest, of course it's rude to be "playing with your phone" during dinner, and while it's sometimes necessary to initiate or answer some communication, to leave the table before doing so is only polite. But rudeness in response to rudeness is rudeness nonetheless, and justified only in the face of extreme provocation; such a minor impoliteness as the one we're discussing is far more pleasantly and effectively dissuaded by a polite response than a rude one -- something which, it seems to me, "I will disallow anyone..." evinces a certain failure to grasp.