Depending on which way you view this situation, either the rock and metal community is slowly falling victim to a very non-metal plague, or a bunch of people are just having a ball with fun music. Recently, Rob Zombie shit on Babymetal haters on Facebook and then talked about how awesome they were live.
Zombie wasn't the first, and certainly won't be the last, to defend Babymetal. We've seen many big names in metal show their support including Metallica, Slayer, Deftones and Limp Bizkit. Carcass defended them, Dragonforce recorded with them and Opeth frontman Mikael Akerfeldt said the band helped ween his young daughter off One Direction. Now, Lamb of God looks positively stoked on meeting the band.
I think what people need to remember here is that this is grown ass adults seeing kids have a ball with the genre they love and it's putting a big smile on their face. On the flip side, this is also kids meeting their musical heroes at a young age and they couldn't be more excited.
So it's just fun all around.