Even scarier, a lot of people in this thread seem to think it's a good thing.
I wouldn't want to know the fury of a disgruntled Founder looking to revenge for a failed YC interview.
Sometimes it is about professionalism. Even though the founder is feeling passionate about their problem space, there are some boundaries you never cross.
In this case it's more of an emotional outburst due to frustration.
If you suppress all emotion with an escalation to a threat of police and security you're going to have a far less dynamic and safe workplace.