Statistical uncertainty means the true percentage can be lower, but it also means that the true percentage can be higher.
Regardless, it may do some good to see that more people (including Black people) are educated GLBT issues. Part of the issue may be that Democrats (at least with respect to elections) have taken Blacks for granted (on race and economic issues) and didn't put in the effort to press them on other issues. Of course, part of the issue may be that Blacks (in media) are quite heavily the butt of sexuality-related jokes, especially on matters of gender-identity.
All, it looks like Whites only barely supported the proposition's defeat. It's not like this group exactly did its job, either.
Again, it may be a better idea to focus on education than on blame (except for maybe those who funded the opposition campaign while enjoying tax-exempt status).