Do you feel those comments are really directed at people with illnesses? I have the feeling that this is what customer support and helpdesk types always say behind the callers' back when its just difficult customers they are referring to.

When someone shouts out something like 'he's crazy' they usually do not mean to refer to that person as actually being 'crazy' Its more of an ill conceived figure of daily speech.

I know its hurtful and its not the proper thing to say but please bear in mind that usually exclamations like this are not in any way meant to be taken personally, even if they seem to sound like it. Basically, the people saying these things just don't have clue what it is they're saying.