I love input, but hate when people try to crush ideas just because they do not like it.
He wasn't criticizing because he didn't like it, he was criticizing because it is potentially lethal. Of course you are welcome to play around with live 120/240 volts if you feel so inclined, but IMO suggesting that it's safe for people to tinker with live AC power is not responsible.
Tinkering is about having fun and exploring possibilities – it is an essential element of Arduino. But it has no place where potentially lethal voltages can be exposed.
Should the general hobbyist that has never worked with AC before use this? absolutly not!