This,all of it.
It a matter of would wields the gun. A gun can be used to kill or not deping on who uses it. People use guns to defend themselves. If your going to ban guns you might as well ban knives becasue you can also kill people with it.
Would technology be like that of movies such as flying cars? Would soceity have changed or would it still be the same as it is today? Would space travel be possible?