It might be a cultural thing, but I have never experienced this. I was a small kid as a child, and I always stood up for kids that were bullied, sometimes by other kids much bigger and older than us. It never backfired.
Same thing the few times I, as a young woman, was harassed by men who couldn't take a no for a no, and every single time, at least one guy came over to ask if I "had a problem I needed him to take care off?" Never backfired for any of them either.