The yuri fanboys are equal to the yaoi fangirls, so what's so confusing about that? A lot of boys like gay girls, and a lot of girls like gay boys...
In a way you're right but I'm going to have to point out a flaw in your logic, and it has to do with the differences in how guys and girls brains work.
I base most of my confusion on the fact that most of the yaoi fangirls I've met are straight.
Most guys like the idea of two women together because in the back of their mind there's always a chance of a 3way, doesn't matter if it's drawn, animated or live, the fantasy is still there. This is the reason that most guys like lesbians. Ergo, you will have some yuri fanboys.
Straight girls aren't wired like that. I don't know very many straight girls that would find the actual act of being gay any bit exciting (in fact most of the ones I know find it repulsive), yet they can idolize a gay relationship. Now many, MANY of the straight girls I know have admitted to having at least an occasional bisexual crush or thought. Again, logical reasoning for yuri fangirls
Now this is of course all from a straight perspective, I can't comment on a gay/lesbian perspective because I'm not wired that way
If someone wants to enlighten me I'm all for it, but I have yet to get a solid answer on the subject