Some people are more sensitive to smells than others. I wouldn't blame the bus company for my olfactory sensitivity, but I know I would have difficulty being in a room with someone who hasn't showered and it would be up to me to move or hope the other person is aware of themselves and doing the best they can. That's all you can hope for but they have the right to take the bus if they have the money.

Also you don't know for sure they are homeless, they could work a night job in a dirty job and have no other means of transportation. They could be homeless, but maybe not. Many homeless people cannot afford a house to shower in, but they are paying for a gym membership ($30-$50 month) and living elsewhere but it affords them a daily workout, swim, social life and shower without anyone else being the wiser to it. You just can't label someone homeless without truly knowing.