Don't kid yourself. I can imagine Bob being very intimidating in real life. First of all, while we can quibble about his size, he's definitely a big boy: just look at how he towers over Anita in the infamous hoverhand pic. Second, and more pertinently, when he's not wearing sunglasses he looks crazier than a shithouse rat. There's something very off about his facial expressions and demeanor (and at this point I take it as a given that he's on the spectrum somewhere). Add to that his obvious anger control issues, and I can definitely see him menacing some poor mayonnaise ghoul who doesn't know any better.
I'm sure he's got a glass jaw, too, and any real fight would end up with him squealing like a pig in a wallow, but I could see people crossing the street to avoid him.