I am not denying the existence of this or any other definition. You're arguing with yourself on that front.
We're stating the fact that that specific usage/definition is not really used at all anymore, to the point that "intercourse" is generally used for the other definition of sexual activity. "Public intercourse" is significantly likely more to be read as "public sex", rather than the intended meaning of "public discourse".
It is perfectly reasonable to suggest a correction, because communication with people is about understanding... not being technically correct to win an argument.
We're stating the fact that that specific usage/definition is not really used at all anymore, to the point that "intercourse" is generally used for the other definition of sexual activity. "Public intercourse" is significantly likely more to be read as "public sex", rather than the intended meaning of "public discourse".
It is perfectly reasonable to suggest a correction, because communication with people is about understanding... not being technically correct to win an argument.
You can check out the usage of these two bigrams via google ngram yourself: https://books.google.com/ngrams/graph?content=public+interco...