Freedom of choice is a broad term and includes several ideas associated with feminism (such as reproductive choices), but it has a couple of specific usages in geek circles which defend sexism:
- that low numbers of women in geek activities are simply a matter of women exercising freedom of choice as to their career and hobbies and that no one should criticise such choice, since it is an example of the goals of feminism that women be able to freely choose careers
- conversely, that sexism in geek activities is not a problem because complainants could choose to avoid that conference/hobby/person in future
The two arguments oppose each other: the first says that there are simply less women geeks because of prior choice, the second that there should be less women geeks (or feminist geeks of either gender) in many areas because they should be avoiding communities that they don't like, rather than trying to change those communities.
The term "choice feminism" is sometimes used as shorthand for the attitude that women should be able to make any choice they want, and that doing so is automatically feminist. For example, "I'm a woman and I choose to be a stay-at-home mother. It's my choice, and I made it freely, therefore it's feminist." Or to give a geek example, "I'm a woman and I choose to cosplay Slave Leia, so that's feminist."
Choice feminism is sometimes criticised for failing to take into account the complex social pressures in place when people make choices. Choices are not made in a vacuum, and some choices women make are closely aligned with anti-feminist ideas in the larger world. Unfortunately, it can sometimes be hard to differentiate criticism of an individual woman's choice from criticism of the wider social context of her choice.
Feminists have pointed out that although women can choose a wide variety of things these days, not all those choices are equal. Some are harder to make because there is more pushback against them. When women have a hard choice and an easy choice, they often choose the easier one, for very good reasons. This ties back to the idea that "women don't choose to go into computing" or whatever. The choices they have available to them aren't equally easy to choose, and so it's not a fully free choice.
Although it is wrong to say that any choice a woman makes is automatically feminist, it's also wrong to say that women who choose the easy option in our kyriarchal society are necessarily anti-feminist. Women generally need to weigh the difficulty of the choices they make against other considerations like existing relationships, their ability to support themselves and/or their families, their mental health, etc. So it is perhaps better to say that feminists can and do make a wide range of choices, and can still be feminists despite that, than that all choices are equally feminist in and of themselves.