It's just another off-shoot of the ever-expanding police state that SWAT raids are so common. I'd be willing to guess that at least 90% of SWAT raids are done for the purposes of perpetuating an immoral drug war. These shows of force are orchestrated specifically for the purpose of showing dominance over the citizens to engender fear and respect for authority.
Though undoubtedly not a pleasant experience, SWAT raids are often necessary in certain situations. When a raid occurs, it is usually done to diffuse a situation that poses imminent danger to the innocent people surrounding it. While the raids may cause some unrest in regular citizens, they exist to protect them from unrecognizable dangers.
SWAT raids do not cause regular citizens undue stress and fear. Maybe if the person is living right next to a house that is getting raided they will be frightened, however SWAT is around to make citizens feel more safe. They are constructed to take down criminals and make places safer, and that is what they do - they just need to do it with force occasionally.
Unless a SWAT team is entering my house, I do not find them stressful. When I see a SWAT van I just know they mean business and I better get out of the way, It's not like I see them often. In our neighborhood we had a SWAT team bust a house down the street for drug activity. We were never so glad to see them arrive. It was stressful knowing that they occupants of that house were throwing trash on our street, hitting our cars, ruining our lawns and bringing drug traffic to our street. I do not find SWAT operations stressful or fearful, unless I am the target. I find them a comfort knowing they are here to protect my rights and my property.