> There is zero science behind this.

I was curious about this so I did a little searching. I found some studies showing that resistance training has lower injury rates than contact sports, and youth resistance training in particular is safer than pretty much any other athletic activity. But I didn't find any studies that covered bodyweight strength training, so I couldn't evaluate GP's claims. Regardless, given the low injury rate for resistance training, I think it's fair to recommend people lift weights, and I mostly agree with your last sentence.