No, I think they're saying that sexualism is to a person's sexuality as sexism is to a person's sex.
However, a quick look at b.g.c. suggests that is very much a minority meaning, to the extent that it might not even meet CFI. The majority meanings appear to be synonyms for sexuality (for which it may be a precursor, and which is its meaning according to OED2+) and sex addiction (cf alcoholism). It is also used as a type of philosophy (which the OED entry leans slightly towards) and as psychology jargon of which I could not quickly deduce the meaning. All in all, it should arouse a range of editors. --Enginear 22:28, 11 January 2007 (UTC)