The problem I have with this situation is that by marrying someone, you're committing yourself to that one person, no matter what happens. Cheating is cheating. Luckily for us, God gave us hands so that we could fulfill our sexual needs. Women can practically shove anything up that hole of theirs and get off.. and now men have those nifty little Fleshlights.
The point is, it's still cheating. I would never leave my girl if she was disabled and I certainly wouldn't seek another partner. Then again, my relationship isn't based solely on sex.