Pairing Issues

It seems to me that all canon-warping pairings are not created equal.  For some bizarro reason, I find that pairing a characters with someone outside of their canonical "destiny" feels more transgressive when the pairing isn't crack.  Taking an indisputably "het" character and putting them in a yaoi or yuri pairing, or pairing two characters Because I Feel Like It (see: "By Any Other Name") is something I'm comfortable enough with.  Taking a "het" character and having them shack up with a totally plausible het choice with some canonical justification feels... dirty?  Feels like I should expect to get mauled for publishing it?  It's like it falls down some sort of fan-fictional Uncanny Valley and from there goes right to the Creepy Zone.

And no, I'm not carping about Catria/Marth again, though I have this problem with that particular pairing.  There's another FE3 hookup I'm working with that has, IMO, even more justification than C/M, and on some level I feel like fanboys and girls ought to beat me with sticks if I ever publish it.  Which is stupid, because every single day fan-writers publish stories featuring pairings that warp, shred, and blast canon.  That's part of what fanfiction is about, man.  I see the potential for this pairing in the text, I'm exploring it, and I shouldn't have to justify it to anyone.

Anyone else have this problem?  Anyone else find they're comfortable with something that is gleefully, unabashedly non-canon/crack, but not comfortable with something plausible enough to be almost-canon?