Well... if there are only two alternatives, then naturally you have to take the one that saves your life.
However, I think there are a lot of things you can do about bullying, and moreover, there are many alternatives to homeschooling. Start a charter school. Commute to a private school, if you can get a scholarship. Apply for a waiver to go to another public school. Etc. IMO homeschooling should not be about withdrawing. It should be chosen out of the many options because it fits your child and your family best.
But I also think that parents who have time to homeschool could also consider the option of getting involved in the school ahead of time, being proactive, starting anti-bullying programs, pushing zero-tolerance policies, being advocates for bullied kids and making sure that all the kids get the help they need. That is really a lot of work, but after all, so is homeschooling.
Now, homeschooling is truly a better option for some kids. I believe that. BUT it's not the best option for all and it's not an option for some. And we do have some responsibility to all children--that's my opinion.