Wrong! Wrong on so many accounts. What if said expression is the only phrase in English a foreigner knows?is like saying, "I cannot speak English." It disproves itself!
Heck, if I were to travel to a French-speaking country right now I'd look up the phrase "I do not speak French" to warn people I may have to interact with in that country that unless they speak English or find a way to communicate with hand signs, notepad drawings, or what have you, that I will NOT be able to understand them.
So, saying "je ne parle pas français" makes me a French speaker now? Give me a break!