Markus, i really do like your attitude
I have experienced similar 'events', and it does not only imply disabled persons of any age, but also insults against people from abroad.
I have only recently learned to speak up immediately, but i admit i probably would not do this in a bus full of skinheads. Chicken-hearted, i know.
The thing is, if only one person speaks up, most others suddenly support, but it seems to need some .. seed chrystal.