I agree that there is nothing worse than being called an it.
But even in spite of that, I can't help supporting unisex bathrooms because, while I sympathise with an ftm's desire to be seen as fully male and I sympathise with an mtf's desire to be seen as fully female, I have to keep seeking for my own place in the world.
I had to go to the washroom today at the mall while I was doing some banking and stuff. The gender neutral handicapped washroom and the family washroom (both separate entrance for one toilet and sink) were full. I'd had a soft pretzel with butter and salt on it and my fingers were sticky. All I was doing was washing my hands--I didn't even go past the sink divider that separates the sinks and cleaning area from the actual toilets. I was wearing some loose cargo pants, a folk festival teeshirt and a ballcap. I was bound, but I was in no way trying to "be a boy." As soon as I walked in, a mother with two little girls grabbed her children away from the sink, their hands still wet, and dragged them out. An elderly woman stared at me until I was done washing my hands and then said to me "For shame. You shouldn't be in here."
I don't feel safe using the ladies' room at all, when I am dressed comfortably. It makes me nervous and upset. Unfortunately, OCD means that I can't leave my hands sticky, so I had no other option right then.
Personally? I think unisex washrooms should be universal and we should, as Elizabeth already suggested, have little rooms with toilets and a central washing up area.
Of course, I know how important gender segregation is to many people here, so I doubt that will ever happen.