Thank you for posting this. This issue happened to me for the first time last week - I thought my account had been hacked. I had no idea how a rouge spammy event got added to my calendar. I ended up resetting my password and spending over an hour pouring over other aspects of my account to make sure nothing else was compromised. It's mind boggling to think this could have been because of a spam message.

This is actually something that has been annoying me for a while. Your solution works and should be implemented. Hope Google listens.