You say you read the article yet you make no attempt to show why it is wrong, you just defer to your initial statement. That doesn't prove it is wrong. 

No one is denying that the first half has an effect, it does have an effect but you are falsely claiming that because it does have an effect that it is therefore the only reason allowed for firearm ownership. If the amendment read that for having a well stocked library, books must be legal, would you then claim libraries are the only reason for books to be legal? No, that would be an improper reading based on English grammar. The clause is there but it is not exclusive no matter how much you would like it to be.