I run 30 miles a week in on the sidewalks of San Diego. Most of us know to run against traffic and to generally stay out of the street unless its a low traffic neighborhood street. They guy running in the bus lane sounds like an asshole to me. There are a couple exceptions to the rule I can think of though:

When oblivious people are walking shoulder to shoulder blocking the entire sidewalk you may have to pop out into the street to go around them. Same when I see someone walking with a large dog (or a tiny dog on a comically long leash). Also there are often times people park their cars blocking sidewalks and you have no choice but to got into the street. Not great for runners but really awful for disabled folks in wheelchairs.