I can't say the police overreacted, since this article doesn't give much info on what they were told. And there is no mention of there being a SWAT team involved, only police with assault rifles. I don't know about that area, but around here, every patrol car has an assault rifle or shotgun, and most have both. If they are contacting an armed subject, or someone reported to be armed, the procedure is to call the subject out if possible, with at least a couple of officers ready with rifles to shoot from a safer distance in case the subject comes out shooting. The rifle is quite appropriate in this situation, and is far more accurate than a pistol from a distance.
I think the tree trimming crew overreacted though. Even if they saw an actual gun in the guy's waistband, if he didn't make any indication that he was going to use it, there was no reason to call the police. Reading the full article, it sounds as if he told the guys not to cut his trees, and they agreed, so he went back inside. Problem over.