"But I also get a little angry when I cant 'see' a disability. "
sorry I'm confused - you say your uncle had Parkinson's yet you get angry when you can't "see" a disability. my mum was diagnosed with Parkinson's Disease 10yrs and had to give up work at the same time, probably had the symptoms much longer - was just put down to other stuff.
Now she's pretty bad - and you can see that she's disabled - but 4/5yrs ago you wouldn't have really know had you looked at her. She didn't have her 'stoop' and was still pretty mobile on her feet. The shakes were generally under control with medication so at a glance she looked perfectly "normal".
However at home she'd be falling alseep at strange times (medication), couldn't do her buttons up, was no longer able to do her beloved cooking/baking and "simple" tasks such as getting in and out of the bath, or changing the light bulb were impossible. She couldn't write anything properly anymore because of the loss of fine motor control - so despite looking "normal" she was most definitely disabled.
We have someone at work with it too - on a 'good' day when his mobility isn't too bad you'd just think he'd got a bit of an 'old age shuffle'.