I learned a little Esperanto the other day (http://en.lernu.net). What a great community and a very interesting language. Speakers of one of the Romance languages will find it easy to learn as the lexicon derives heavily from Latin (in a more recognizable, Italian form). I wondered why Esperanto had never really caught on as an auxiliary language (i.e. a language that can be spoken between two people with different native languages). I suppose it's due to the fact that French and English have often filled that role. But, that is a whole other post in itself.
One of the discussion forums had a posting about gender in Esperanto. French and English aside, this might be the real reason that the Esperanto community isn't larger than it is. No, not because of it's handling of gender. Because of posts like that one. So many assumptions made, so many linguistic misunderstandings.
Let's step back a moment and look at gender in a language. First of all, words don't have gender. Or, let me put it another way: words don't have gender. Gender is a biological trait. For reproduction. Words don't reproduce.
Most languages, however, arbitrarily call one group of words "masculine" (the group which has endings that match the word for "man" in that language). Another group will be called "feminine" (the group which has endings that match the word for "woman" in that language). Sometimes there's even "neuter" (for words that fall into neither category).
But, the words themselves don't have any gender. It's just a term for convenience. It helps us to identify that group of words. The actual term in Italian would be "genere" which means "type". Words don't have gender. Look at one with its clothes off sometime if you don't believe me.
Now that we have that out of the way, let's look at the poster's complaint. The idea was that Esperanto is sexist because a few words have the suffix -in- added to them to indicate biological femininity. Of course, it's just as easy to say that all words in Esperanto inherently contain the -in- suffix and that the omission of the this indicates biological masculinity.
Even readers of this blog (I'm assuming a certain amount of interest in linguistics) will probably find this very arbitrary and semantic. And that, my friends, is the point. Nit picking like this raises a barrier around your community. I could be wrong, but I'm guessing that these kind of assumptions and agenda pushing get in the way of the wider adoption of an interesting language.