I don't think too many people will discredit England if they do win (I certainly wouldn't), but the point here is that they shouldn't even be allowed to be in a position to win from here. It's the leinency of the format which I feel most people are against. It also reflects badly on the quality of cricket played, the world cup winners should have won most if not all of their games in the world cup, that's how the format should be set up, these backdoor entry wins are rather lame, even if they make for a "great story".
England were in the same position last time around IIRC, at least in 2011 they lost to smaller teams and competed with the bigger wins, still not a fan of this quarter finals garbage, but at least you could somewhat justify an England win had they won in 2011. This time around it would annoy most people if they did indeed pull of a miracle, England haven't merely lost, they've been owned, well and truly.