Promoting Ikebana as a form of art (Western art) created a great Ikebana boom after the war with tens millions of Ikebana students. However, the term "art" was problematic. Art is a Western concept introduced to Japan after the Meiji era. Although Tenshin Okakura proposed an influential definition of art, it is a bit hard to understand for the general public. In addition, since Modernism it seems that even Western specialists cannot agree on what art is.
Stating that Ikebana is art means that Ikebana becomes ambiguous for the majority of Japanese people. Sofu Teshigahara insisted that Ikebana is free self-expression but that simple definition was also confusing. It's easy to see how this could cause some problems sooner or later.