From Google's blog post:

"Strong email authentication helps users and email security systems identify and stop spam, and also enables senders to leverage their brand trust."

Another way to stop spam is to make everyone pay to send email. Spammers, and brands, can't afford to pay to send marketing emails en masse.

Thank you for trying to defend Tor. Can you share some of what the parent was ignorant to?

Does it cost less than 5 dollars a month to create a Tor node?