(1) Perhaps the MMN guys could not read Morse, so they would not know what the CW activity was.
(2) I agree with Karl on this one. Nobody has prior right to a frequency, whether it is a “regular activity” or not. If the usual net frequency is already in use, the net controller should find an alternative frequency which is clear. End of story.
(3) It is true that there is no objection to using CW on any frequency within the 20m band. That applies here in Europe too.
73,
Walt (G3NYY)