Hearing viewers find low-quality, incomplete audio content unacceptable. Similarly, captions that are inaccurate or contain spelling and grammatical errors are unacceptable to deaf and hard-of-hearing viewers.
I suggest avoiding the comparison and explaining the problem. The degree of "acceptable" vs "unacceptable" is subjective, and may undermine your point. Suggested wording:
"Captions that are inaccurate or contain spelling and grammatical errors are distract and distort the content, thus disadvantage deaf and hard-of-hearing viewers."
+1, also in some circumstances a low-quality audio might be OK (video shot on a phone, observing something) while in other circumstances it is not OK (blockbuster movies).
Current text:
I suggest avoiding the comparison and explaining the problem. The degree of "acceptable" vs "unacceptable" is subjective, and may undermine your point. Suggested wording:
"Captions that are inaccurate or contain spelling and grammatical errors are distract and distort the content, thus disadvantage deaf and hard-of-hearing viewers."
(this also further reduces the text)