Man arrested for 2x4 labeled "High Powered Rifle"
I think you need to prove two things before you ban something: (1) it's unnecessary, and (2) it's proven to be more dangerous in public use than other legal alternatives.
The second half of your post proves to me that you recognize principle (2) as well. Even though ju-jitsu is unnecessary, you support its legality because it's not proven to be more dangerous than other hobbies in the hands of civilians.
Where I start to find serious inconsistencies in your post is when you start talking about banning modern sporting rifles SPECIFICALLY. Because, as I've pointed out repeatedly, in real life, they're used to murder far far LESS often than handguns. They have NOT proven to be more dangerous in the hands of the general public than other firearms.
Like offtopic versus boxing, they "seem" more dangerous than the alternative (that's why offtopic was banned in many US states in the 1990s), but casualty statistics simply don't back up that gut reaction.
So why are you so adamant about banning MSRs given affirmative evidence that they're used far less frequently for murder per firearm or per owner than other sorts of firearms?
Modern sporting rifles are to firearms what mastiffs are to dogs. When you take a look at them, they seem like the most dangerous thing out there (a mastiff is definitely more visually intimidating than a pitbull). And there's no "need" for a dog that big with jaws that strong. And their original purpose in the middle ages was war and fighting. But when you actually look at statistics, mastiffs are far less likely to be involved in violence than other breeds (particularly pitbulls and rottweilers, the handguns of dogs). So would you support a mastiff ban, even though it's been proven that in real life they're responsible for fewer casualties per capita than less "theoretically lethal" dogs?