Of all arguments intended to corrode the feminist movement, “sex positivity is a slippery slope leading to incestual marriage” has to be one of the most ridiculous.
You’ve posed a question asking whether a feminist would support the legalization of incestual marriage.
First, how did we get from sex positivity to marriage? Like many controversial issues, I can’t speak for all feminists, but consensual incest is such a rare phenomenon that in most cases of incest, only one person is consenting and therefore is considered rape or molestation.
Because of this, incest is not usually a friendly term in the feminist community, or in general; however, in those rare cases where it is two consenting and of age individuals, yes, most feminists would encourage that they have safe sex rather than unprotected sex.
People, like you, often miss the point of sex positivity. Many have learned over time, from an evolutionary and logical standpoint, that if two people want to have sex, they will most likely find a way to make it happen.
When they are forbidden to do so, impulse decisions and mistakes are more likely to occur. Why not educate people on all of the risks and advantages, the pros and cons, of sex and then put the decision in their hands?
The sex positive movement might be broad and a little extreme, but it is one solution to the sex education deficit in this country, particularly in North Dakota, This state still teaches abstinence-only, biased sex education as the most common approach in high school health courses.
You also mention “feminists ‘promote practices’ like homosexuality, promiscuity, abortion, etc.” It should be noted that sexuality and gender are not “practices.”
You would never say that a woman “practices” being a woman, just as a transgender woman is not “practicing” their given gender.
Sure, BDSM is a practice, but do feminists “promote” BDSM? No. Again, sex positivity is the concept that sex should be safe and consensual. Period.
You make the final “groundbreaking” comparison between the opposition of incestuous marriage by feminists and the opposition of gay marriage by most conservatives, which isn’t valid considering the lack of collective stance by feminists on the subject of incestual marriage.