If the Swat team response to an unverified phone call is to put people's lives at such severe risk as you describe, the problem is with the police, not the teenage idiot who placed the fake calls.
The issue is two-fold:
1) 99.9+% of all calls that result in a 'SWAT' response are legit. The swat response might be overkill, but the call itself is honest and legitimate. Expecting police to prove that a call is real when the vast majority are real is going to be a far greater threat to peoples' lives and safety than taking such calls at face value.
2) Police responses can be overkill. In some cases, police have been known to open fire before even asking people to drop their weapon.
To blame police for the results of a swatting call is like pushing someone randomly into the street and then claiming that it's all the fault of the driver for not stopping in time. Although some blame may be assigned to the driver for not keenly watching for people darting onto the roadway, it was the push which caused the initial peril, and the impact was the completely foreseeable result of the push.