In the context of the above discussion, "criminal" is the person who is using the gun for criminal activities, i.e. murder, extortion, etc. I can see the arguments that such criminals should not be in possession of a firearm. I can also see arguments that power-hungry cops should not be in possession of a firearm either. But as a private citizen, who is neither, why should I surrender a gun? I am not a threat to anyone.
Why should you have a gun? It is a personal preference. Like art or poetry. You are free to want whatever you want. If you do not like/want guns, please do not have them. But, please do not impose your preferences on others.