Many English speakers do not know, or are not fluent in, any other languages. We therefore should not feel entitled to criticize the English skills of someone who took the effort to become fluent in English as a second language.

Agree completely. But still I'm typically impressed with how well they can communicate, and so have little reason to criticize to begin with.

On a slightly related note, I've had the opposite problem of people thinking I'm not a native English speaker (when yes, I am one). This only happens for in-person conversation: for some reason, they think I'm from Europe, usually Germany. (I speak German, but only from having learned it in school and having done a short exchange.)

It happened again recently: I went to a meeting of a group I hadn't been to before, and, as is common, someone asked me where I was from, and was suprised to hear my answer of Austin, TX. He said he assumed I was from Germany from how I talk, which I would dismiss as a fluke except that he was the ~15th person to say that. I certainly admit that I don't sound Texan at all -- never picked up an accent for some reason.

(I would link my youtube page, but I'm not sure any of the videos give a characteristic example of what I sound like in conversation.)