In my opinion, the only difference is that Feminism is biased and inaccessible to everyone.
When trying to spread its ideals to men and other women who are not as biased as a feminist is, it makes people angry and therefore does nothing for the spread of humanism, which is the true strive for equality.
Feminism seems useful to me only to a select group who share bitter experiences towards men. It is useful to have a support group to talk about things that are troubling you and how men have hurt you, but feminism is and always will be the biased and segregated from humanism which doesn't in and of itself help the humanist cause.
What are your own thoughts on the difference between humanism and feminism? Clearly one can be both, but is it right for someone pursuing humanism to pursue it in the name of feminism?