Funny I actually started bike commuting a couple years ago out of necessity and then it became a hobby (though it is still a necessity). I decided to go to engineering school when I was 30 years old even though I had a wife and child on the way, giving up one car has been a critical element in making it financially possible. One thing I have been offended by is when people (mainly people in cars) have treated me like I am some kind of an idiot for being on the road on a bicycle. It just happened yesterday, I was in a turning lane, doing everything right, I was well lit, hand signalling my turn etc. and some jerk yelled as he passed by "get the F*** off the road". That is offensive, because I don't really have the option (financially) of getting off the road.

As far as homeless people being offended by me as I pass by, I don't really know much about that. I guess I do mostly commute on an old bike and I wear basic street clothes (sweat pants) so I don't look rich, but I also don't look homeless because my bike has lights and I wear a helmet. I have found many of them to be friendly and courteous as I ride by each day, they often smile or say hello and I do the same. I have actually found that many of them are more worried about offending others than they are worried about being offended. Sometimes they apologize needlessly if they inadvertently cause me to have to slow down or something.