It seems to me the issue comes down to one of fear. Do we walk with trust and confidence in God, or do we walk in fear of the world? Do we let the world define our Christian walk? If the world has guns, we need guns - is that the proper Christian perspective? is that what God wants and expects? is that the message God wants believers to communicate? Is a church with armed deacons, metal detectors and stern warnings out front really what God wants?
As a Christian, I have to believe that what occurred in the Texas church was God's plan for the victims on that day. How that incident fit into God's larger plan, no one knows. I wouldn't demean the victims by even suggesting how it might have fit. But if I didn't believe the incident was in some way God's plan for the victims, it seems to me the entire framework of my belief would collapse. I have to believe that if the church had had armed deacons, metal detectors and stern warnings out front, the incident would have unfolded pretty much as it did - because it was God's plan.
Is there an inconsistency in using the locks on our homes and cars? Probably - I know people who don't. If there is an inconsistency, it is not one that would point in the direction of armed deacons and metal detectors in churches. It would point in the direction of asking ourselves, "Why do I do that, if I am walking with trust and confidence in God? For all my Christian prattle, do I perhaps not have the faith of a mustard seed?"