An important fact about ACORN:
If they receive a voter registration card that's been filled out, they are legally obligated to turn it in, even if it's obviously fake. This is to prevent, say, my friends and I from setting up a voter registration table outside our local right-wing mega-church, then throwing out all those registrations.
In many of the states where they're being investigated, they actually put the forms they thought fraudulent into a separate batch and flagged them as such when they turned them in, but their flagging was ignored.
Here's the deal: If you think it's good to have as many people as possible registered to vote (and voting), then ACORN is good, and the fake registrations are just a pain in the ass for county clerks to deal with, since fake registrations virtually never lead to actual votes being cast. If you don't, then ACORN is bad.
And if your candidate is losing the race for President, and you're basically losing ground all over the place, then ACORN is a convenient scapegoat that will allow you to a) claim the Obama presidency is illegitimate and b) avoid examining the problems in your own party that led to your defeat.