People with certain disabilities often have heavy disability accents. Their speech can sound very different from the way most nondisabled people speak.
People with disabilities that affect communication are often pushed into separate programs, particularly in adulthood. Even when they are in the…
Many of these disability accents are very specific and caused by anatomical differences. For example, severe cleft palates can leave a speaker unable to differentiate fricatives when speaking (even when the cleft was corrected surgically) — thus, “s”, “sh”, and “h” (when emphasized) sound more or less the same. In English, this can cause difficulty for majority speakers to understand them at times.
However, this is not any more difficult to understand than a Japanese speaker who can’t easily pronounce the differences between “l” and “r” or “f” and “V”. While I am sure (non-european) foreign speakers receive some similar treatment, the bottom line here is that it’s only the disability, not any objective difficulty in understanding, that is causing this behavior.