I made this point on the main page but I'd like to reiterate it here, because it seemed like a point that I didn't see getting made.
I would never want to be the boss of a former bully. I could probably deal with it, but I wouldn't want to, and nor should I have to. Bullies are awful people, and what they do to you doesn't necessarily go away. It's part of your identity. Being reminded of it isn't fun.
I don't wish ill will to my past bullies. I wish for them, just like I wish for anyone, some peace in their life and that they're not bullying anyone anymore. However, they can do that in their own time and space without making me think about the bad things they did to me. Maybe this is a cop out way of saying I can't actually forgive them, but distancing myself from someone is healthy for them just as much as it is for me, and if that's what it takes to forgive them that's what I prefer.
Edit: Per Jenny Apple's point, I'm speaking to the relationship an individual has with someone who bullied them specifically. I realize the ad might be speaking in generalities (though getting revenge on bullies in general just sounds a little weird). If someone I met on the job who bullied others in the past wasn't being a jerk any longer that wouldn't be the same thing.