There's a term for this: Victim Blaming.
It's one thing to not be so sensitive when it comes to jokes or teasing, but this requires a maturity that a child does not yet have.
A feel as though a lot of people that say those things haven't been victims of bullying, or maybe, at least, not the a certain extent that others were (I know I'm treading very close to a No True Scotsman with that statement).
I was bullied when I was a child and it was BAD. I can't really express how EVIL the bullies were. Like something out of a horror film.
Edit: I'm a little confused by the replies - I re-read my comment to see if anything was ambiguous. I'm saying that bulling is way worse than people think. Maybe it was unclear that I am agreeing with the comment I was replying to, not opposing it?