I liked the movie, but I don't think that the idea was to necessarily like either of the lead characters. Just laugh at them for their bizarre dance to see who could get the most attention. I imagine a sequel set 10 years into the future where Bob is now the esteemed arrogant psychologist and Dreyfus is a nutty patient that drives him insane...and they switch places again.
It came off to me as "Let's laugh at this guy because he has a mental illness!" - granted, the movie's pretty old by now, but I think that's the part that bothers me the most. (As with any movies with that general setup - "Let's laugh at Napoleon Dynamite because he's a social reject!" "Let's laugh at how the blind guy and the deaf guy could have totally caught that bad guy if they had been sighted and had normal hearing!")
I didn't get the same impression they were making fun of the mentally ill. I guess to me the movie was making fun of people who pretend to have mental illnesses -- i.e. drama queens. That's not quite so offensive in my book. He was afraid of change, common life situations, illness, and death; he'd get attached to pets and people; he's self-centered. Bob could quite easily conquer these fears when he decided to, which means he wasn't really mentally ill, just immature, which is probably why the children in the movie were especially fond of him.
For See No Evil, Hear No Evil -- granted Richard Prior made a career of being offensive, kind of like Mel Brooks -- but why couldn't
a deaf person partnered with a blind person solve a crime? Sure it was a screw-ball comedy but I'd call them role models
...well, OK, sort of.