Thats surprising to know. I know many people, some of them my own relatives, who are worshippers of Lord Ayyappa, yet they worship other Hindu gods and celebrate all Hindu festivals. This is the first time I am hearing something like this. In anycase, Lord Ayyappa (http://en.wikipedia.org/wiki/Ayyappan) is Shiva’s son. His worshipers are invariably Hindu!
you are correct — I meant to say Ayyavazhi, not followers of Lord Ayyappa.