http://www.salmonriver.com/words/nancy/maia.html
May Day Origins... by Nancy Sherer
The earliest known picture of a May-pole is taken from a drawing
of a window in Betley Hall, Staffordshire, England,
erected in the mid-1460s during the rule of Edward IV ...
May day might have been adopted by Communists and Marxists as a day to spread their BS, but I don't think that has any bearing on the origins of the holiday.