First, you're absolutely correct about the "If you trust God..." empty arguments. Based on that same logic, a Christian should never go to a doctor, own a fire extinguisher, etc. As for a few scriptural references:
- When Nehemiah returned to Jerusalem to rebuild the walls around the city, he instructed his people to carry "their swords, their spears, and their bows" in order to protect themselves against the threats from their enemies (i.e. they adopted Open Carry). He then says “Do not be afraid of them. Remember the Lord, who is great and awesome, and fight for your brothers, your sons, your daughters, your wives, and your homes.” (Neh 4:12-23)
- When Jesus was betrayed in the Garden of Gethsemane, and Peter drew his sword to protect him (cutting off someone's ear in the process), Jesus told him to put it away. However, Jesus didn't rebuke Peter for having the sword, or even from using it in general. Jesus only rebuked Peter because Peter was interfering with God's plan - "Shall I not drink the cup the Father has given me?” (John 18:11). In fact, Jesus actually instructed His disciples to get a sword if they didn't already have one (Luke 22:36).
- People who hold that "Christian's shouldn't own/carry guns" usually use Matthew 5:38-39 as their reason - "turn the other cheek." However, if you read the full context of that chapter, Jesus is talking about how to respond to those who aren't being nice to you (v11). If He meant a Christian should never protect himself or his family from someone trying to do them harm, He would not have told the disciples to get a sword, nor would Nehemiah have said the same thing to his people.