however, the mistake they made in this situation was that once they barged in and saw that there was no threat, they should have calmed down their testosterone and talked it out with the guy, instead of arresting him.
There was no mistake, they took every precaution they could. What if he had a gun or something (if the bomb threat was an actual situation)? And it seems like they're in an office style building, so he could be one of a few other people, not necessarily the bomber. The guy who called in the "threat" isn't gonna give detailed information on the situation, just "UH SUCH AND SUCH WHO LIVES AT THIS LOCATION IS PLANNING A BOMB PLS ARREST." The SWAT team has zero information on the person they're arresting most of the time.