Gun fanatics use the same logic as creationists to justify their view.
Creationists say that evolution doesn't exist simply because the bible says that "God created man in his own image".
To them this means that God created man instantly, in one stroke, and they insist this is the only possible interpretation.
This one sentence justifies the denial of all scientific evidence of evolution (even though this physical evidence was allegedly provided to us by God).
Gun fanatics say assault weapon ownership can't be limited because the Constitution says, "The right of the people to keep and bear Arms, shall not be infringed."
They define this sentence in one limited, absolute way, (and ignore the qualifying sentence referring the Militia.)
Because of this they insist their right to own these weapons is absolute and any consequences to citizens and society can not be considered as justification for limiting this right.
Both use one simple english sentence interpreted in one simple minded, limited way as justification to ignore reality.