as a cis woman, the last one strikes me as being most true - I'd expand and say that people - especially cis women, and especially feminist cis women - feel uncomfortable being characterised under their privilege (cis) because they might at that moment (on the feminist internet) be preoccupied with the non privileged part of their identity as a woman, and not feel up to dealing with the fact that they have privileges that other people dont because its uncomfortable. Its like how some people might get defensive about being called white and middle class in the same sentence, even though they are. they want to be part of the non privileged conversation because thats what they signed up for. which is obviously a very spoilt and unhelpful attitude, but as you say, you can see how it comes about