Perspective and a cool head are required.
In the Old West they hung horse thieves. Why was that ?
Because in the remote circumstances that people often found themselves, if a man was denied his horse as a means of transportation - he died.
That is hardly the case with most property stolen or vandalized today.
Are you going to shoot someone for spray painting your house ? Really ?
The best remedy in such circumstances is adequate homeowners insurance and some maturity. (Though having a big dog in your yard might also help.) One draws a firearm if they are willing to use it for the purpose of protecting life or limb.
Frankly I can't think of a politician worth posting a sign for, much less 'defending' said politician's sign.