Q. Why do you suppose Jesus would tell the disciples to bring swords, and then they do, and then Peter cuts off someone’s ear, and then Jesus clearly thought that was a dumb move, and heals the guy? It seems like a weird sequence of events.
The events you’re describing happen on the last night of Jesus’ life on earth. At the Last Supper, he predicts Peter’s denial, and then warns the disciples that the circumstances of their lives and witness are going to change. He asks them, “When I sent you out to preach the Good News and you did not have money, a traveler’s bag, or an extra pair of sandals, did you need anything?” When they say “no,” he responds, “But now take your money and a traveler’s bag. And if you don’t have a sword, sell your cloak and buy one.”
It appears that there are some contexts that will be favorable to the life and witness of the community of Jesus’ followers, and in those contexts, it can count on what appears to be spontaneous support as God actually moves in people’s hearts to respond. (This happens, for example, when Paul proclaims the good news in Thyatira and a woman named Lydia is listening. Luke, who was traveling with Paul at the time, describes what happened: “The Lord opened her heart to respond to Paul’s message. When she and the members of her household were baptized, she invited us to her home. ‘If you consider me a believer in the Lord,’ she said, ‘come and stay at my house.’”)
However, there are other contexts that are very unfavorable, indeed hostile, to the life and witness of the community of Jesus’ followers. In those contexts, it shouldn’t expect the support of outsiders. It has to supply its own provisions and it also needs to be prepared to defend and protect its members by reasonable means and precautions.
I think it’s significant that when the disciples reply to Jesus at the Last Supper, “Look, Lord, we have two swords among us,” he answers, “That’s enough.” Many biblical interpreters believe that Jesus is saying it’s all right for the disciples to have some weapons as a deterrent and basic protection in a hostile environment.
However, in the Garden of Gesthemane, Peter moves from defense to offense by attacking first. He also does this in a situation where the disciples are outnumbered and much less well armed than their opponents. Jesus rebukes him and heals the man he injured, in order to prevent a bloodbath.
So it appears that while the community of Jesus’ followers can adopt basic protections and precautions, when it encounters an overwhelming force bent on doing harm, its response must not be to fight to the last one standing, but to be willing to accept suffering as the means of continuing its witness.
Good Question 
Is it wrong to protect the congregation from an evil person that walks in to do harm? Some congregations like in Texas where a parishioner shot the evil guy that killed 2… did he do the right thing?
This is indeed a difficult question. But as I say in this post about the passage where Jesus tells the disciples that they should now sell their cloaks and buy swords, “Many biblical interpreters believe that Jesus is saying it’s all right for the disciples to have some weapons as a deterrent and basic protection in a hostile environment.” But I think it’s important to emphasize that these weapons are meant to be used to protect other, defenseless members of the community against deadly violence, not to spare oneself from suffering for the sake of Jesus if necessary. As one person put it, “When someone slaps you on the cheek, turn the other cheek; but if you see someone slap another person, go over and defend that person.” I know several churches that have openly invited “current and former military and law enforcement personnel” in their membership to form part of a “security team.” The recent incident in Texas is not the only one in which armed members of a congregation have defended the other members against a would-be mass shooter. The issues your question raises seem similar to those considered in another post in which I discuss the two longstanding Christian traditions of pacifism and “just war” theory. As I say in that post, the ultimate question is, “Is there any biblical basis for one human intentionally taking the life of another?” A convinced and committed pacifist might say there is none. Another Christian might argue that there is some basis for using deadly force to protect many innocent lives from being taken. I respect both positions, and I imagine that Christians of good will, with equal commitments to the inspiration and authority of the Scriptures, might ultimately disagree about this. So, as I said, it is a difficult question. But it is being forced upon us by an epidemic of gun violence, and I would hope that all Christians would agree that we should do all we can to end that epidemic.