I'm not trans, but I'm pretty sure lots of trans people do their best to "pass" as the gender they are transitioning to. A lot of that means dressing in feminine or masculine clothing and accessories.
That's not to say some creeps may take advantage, but I don't think it is fair for fear of a few creeps to overrule the rights of people struggling to be who they truly are.
From what I am learning is they have to live as the gender they accept as their own for at least a year before approval for surgery. So someone(not you) stating that if they have the sex organs of a man still then they can not go in is cruel and wrong. If it is a man transitioning to a woman and having to continue to use a male bathroom while dressed as a woman sets them up for ridicule, abuse, humiliation and so much more when they are already going through so much just to feel comfortable in their own body.
As for creeps taking advantage there are already creeps in the bathrooms. Allowing trans people in there does not change that.
Sadly this reminds me of history that was not so long ago. The right to be prejudice against a select group of people based on a physical trait just because some people don't understand or are uncomfortable.