No some people do have a genuine bad reaction to vitamin C. My stepfather is an example and cannot take vitamin C at all. But again , I think it depends on whether it's a genuine reaction/allergy, or whether it may actually be some toxin movement/elimination going on. Even healthy people still have toxins and claim they cannot handle certain things and often don't realise it can be helping more toxins come out.

I guess people would get enough vitamin C in other things that are not as acidic if they genuinely have an intolerance to vitamin C otherwise...

The signs he gets is burning in the eyes etc. It's very bad what happens to him and it seems to be the acid side of it or something.