Sex positive basically means we can have and enjoy sex for reasons other than for procreation within the confines of marriage. It’s advocating for birth control and saying people can and do have sexual for fun and pleasure and even casual sexual relations can be good. There’s nothing inhertantly shameful about a one night stand if both parties know that’s what they want and have fun.  But as always the loud fats have tried to make it about them and body positivity. I don’t think there’s any issue that they try to not make it all about being fat.