That is sad, but for a society where the only real contact or news of a doggy nature for many people is the press it is a natural reaction. People know about guide dogs (seeing eye dogs), police dogs and gaurd dogs. The rest is what the papers choose to report.
How about all you people with PAT dogs (what you call therapy dogs, I think) getting in touch with your local newspapers and inviting them to come on one of your visits? Tell them that this is an ordinary pet dog that is doing something extraordinary and it's really worth a look.