It's legal and within the law to defend yourself and your loved ones with a firearm.  That necessarily means that doing so is therefore not "vigilantism."
.
Many police departments highly recommend that citizens own and practice using firearms, but I tell you what, John-- you let me know when you're getting attacked, assaulted, or violated, and I'll make sure to stay as clear from you as possible, deal?  When assaults and violence take seconds to commit- I'm sure the police are just minutes away.