You are correct about the problems created when too many people live in too small a space, an ever-growing problem as our nation becomes more and more the dumping ground from every war-torn hellhole on the planet. I have said for a very long time that "more people = less freedom". This is only one of the reasons why Thomas Jefferson was of the opinion that
"The mobs of the great cities add just so much to the support of pure government as sores do to the strength of the human body." (Notes on Virginia Q.XIX, 1782. ME 2:230)
Keeping firearms out of the hands of "criminal or irresponsible individuals" makes sense on its face. However, the definition of "criminal or irresponsible" varies considerably depending on who's in charge. From living in California for almost twenty years, I learned that the majority of self-anointed demagogues in that states' quasi-totalitarian government consider anyone who owns so much as a .22lr single-shot is considered "criminal or irresponsible".
They themselves were always immune to this definition, however. Interesting how that works...
The whole of that Bill [of Rights] is a declaration of the right of the people at large or considered as individuals...[I]t establishes some rights of the individual as unalienable and which consequently, no majority has a right to deprive them of. ---Albert Gallatin to Alexander Addison, Oct 7, 1789, MS. in N.Y. Hist. Soc.-A.G. Papers, 2.