Saying "I speak no English" does not mean that they are fluent in English. Giving them grief for this is not a nice thing to do.
Sometimes, phrases like that are the only English they know, even though they don't know exactly what they're saying.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.