It ONLY makes him a d-bag if he never tried knocking on the door and asking them to quiet down, or calling them and asking. If he skipped straight to calling the cops...d-bag. If he called the cops because being a good neighbor and calling/knocking on their door was unsuccessful, then he did the right thing.
Oh, and yeah, OP: Get a gun, or if you have a gun...spend some time at the range practicing. Just in case. Sounds like this guys a wack job.
Agreed. I guess I should have elaborated.