"Pichai said in an email to staff that several Google employees became fearful for their safety and grew concerned about being outed for speaking up at the town hall."

Ridiculous reason for cancelling this event.  

In an alternate universe:
Fearful: "I'm scared--I'm afraid I'll be outed for speaking at the town hall. It may not be safe for me. 
Google: "We've beefed up security. We'll be saying something about this before we start.  However, you are free not to attend and choose to watch the streaming video of the town hall. you feel this way--truly. And we wonder how many of our employees feel the same way and why? It may mean we have work to do in this area. Your input's valuable to us."  

But, no.  Cancel the event!  
Cynical observer: that sure worked, didn't it?  Fearful's cheque is in the mail, as they say.