When I see a black man riding a bike, I always check if it's mine, but then I go home and check my garage and see that mine is still chained up.
Why would you think that a black man was riding a stolen bike?
Dirty black folks are unworthy to be part of society.
Your blanket prejudices about blacks leads you to jump to inaccurate conclusions as when you see a black man riding a bike and wondering if they stole it. This sets blacks on a lower rung than yourself and it's not okay to do that. You need to treat everyone with dignity not suspicion.