I think 'humanism' means something else.

What about 'anti-sexism' ? The OED doesn't seem to recognize it specifically, but it is a perfectly regular formation and, I think, in common use.

The OED says that that 'sexism' is formed on the model of 'racism' and means 'The assumption that one sex is superior to the other and the resultant discrimination practised against members of the supposed inferior sex (esp. by men against women); also conformity with the traditional stereotyping of social roles on the basis of sex'.