A few decades ago the only men dressed as women that were in the news were Drag Queens at gay pride parades. So people made the association. Also, what Badtranny said.
AND ... we don't currently have a "would you date a man thread", but when we did, more than half of the people said yes. Whether some of those were fantasy or not doesn't matter. When people see images of CDers, they are usually associated with the gay crowd, or in T-girl porn while having sex with men. And then there are all the suggestive poses that CDers love to take in their pics, the type of poses that would not attract a GG.