I'm not sure that anyone is saying that "discussion" is off the table.
But, during the discussion, what measures will be most effective. 85% of all gun crimes are committed with a handgun. The vast majority of those aren't "mass murder" types, so magazine limits won't curb them. And, assault rifle bans won't touch them. The remainging 15% are comprised of both shotguns, hunting rifles and assault rifles. Shotguns don't accept large magazines, and aren't assault rifles, so they won't be affected. And, hunting rifles won't be affected by assault rifle bans. What you are left with are hunting rifles that accept large mags, and assault rifles.
Oh the other hand, restricting mag size isn't likley to impare anyone's lawful use of a weapon. There may be some exceptions, at which point there should be exceptions made to the law to allow them in certain instances.
There are a lot more nuances and details here, which I'm not qualified nor inclined to tackle. I simply wished to illustrate and stress that the issues are NOT "banning assault rifles" or "putting AR-15s in the hands of every 15 year old". The issues are very detailed and grey.
There is a line somewhere in the middle that we all draw when talking about who should have guns, when, and what type of guns they should have. Let's try to define the line, and not throw grenades at the extreme right or left of each area - concentrate on the middle.