As proof of this, I searched the opera website for the word "microsoft". Here were some pages from the results:
http://www.opera.com/pressreleases/20011101.html http://www.opera.com/pressreleases/20011026.html http://www.opera.com/pressreleases/en/2002/02/20020212.html http://www.opera.com/press/articles/english.html http://www.opera.com/press/manifesto.html