"Opposites attract" is also pretty much the reasoning for Rarijack, but that is another story. I think Dislestia, if it were to happen, would take quite some time. I agree that 5 of the Mane 6 hate Discord's guts (or at least dislike him). However, when Discord does something seemingly dickish he does it for good or understandable reasons beneath the dickish behavior. In "Princess Twilight Sparkle" he does act like a dick, but he teaches Twi a lesson. Albeit in his own way of doing so. Also, in "Three's a Crowd" he tried to separate Twi and Cadence, but did so because he was jealous, an understandable emotion, in my eyes at least, that proves he cares about the friendship of Twilight Sparkle.
You sir have hit the nail on the head of why I don't hate Dislestia. I find it awkward though because of their enemy status, I think it would go somewhat like this. "Hello Celestia! You froze my ass in stone but I still find yours (spanks Celestias flank) quite attractive! Wanna do something sometime?" He then gets blasted with a solar beam in the face and writes Fluttershy a letter stating "Dear Fluttershy, Don't ever ask Celestia out. EVER!, Sincerely, Discord." The idea of 2 immortal trolls coming together also is pretty funny and can lead to some interesting things. I don't ship Fluttermac because they don't have any moments together on the show and are only brought together because they are both shy. As for Flutterdash, give me some irrefutable canon evidence that RD or Flutters is lesbian and we'll talk.