Someone made an inappropriate joke at too high of a volume.
Somebody else felt uncomfortable and made a mistake in their reaction.
People make mistakes. Couldn't SendGrid have offered the guy a job and apologized profusely.
You could argue that her job is to be an advocate for SendGrid, and this incident has done the opposite. But I assume she was just fired so the ddos would go away.
Also announcing it on Facebook is brutal, even though they may have had no other choice.