When looking at the purpose of something, you do not look at the reason why people buy it, you look at how and why it is MADE.<quoted text>
You say guns are intended to kill. Period.
The statement makes too broad of an assumption. It implies that this is the most important reason why guns exist in our society.
Guns can be used as tools to make sounds (like in a race), to shoot at paper for entertainment and to hunt.
You cannot make the broad statement that guns are designed to kill and maintain logical integrity.
Guns are made to be used as weapons.
By the logic you use, I should be allowed to buy grenades because I want to use them to go fishing.