The best rule of thumb is that you should not pull a gun unless you are legally and morally justified in using it. That is not to say that if you pull a gun you must use it as the situation can and often does de-escalate with the presence of a firearm.
Most people would say that the litmus test for pulling/using a gun legally and morally is whether or not you had reasonable fear of death or great bodily harm. As frustrating, disrespectful, and disgusting as someone spraypainting pictures of male anatomy on your home is, I think we can all agree that it does not represent a threat of death or great bodily harm to you or your loved ones. I think that perhaps some cameras would be a better device for dealing with vandalism than a gun would.
Smith, and Wesson, and Me. -H. Callahan
Well waddaya know, one buwwet weft! -E. Fudd
All bad precedents begin as justifiable measures. -J. Caesar