Obviously, there is nothing "wrong" with Republicans helping to put Nader on the ballot in many of the key "swing" states. That being said, there is clearly something unseemly about Nader accepting that help, he has to recognize that he is being used as a pawn by the Republican party to help re-elect Bush.
Here's the question I'd like to know, though. If the Republicans think it's that important for our democracy to get Nader on the ballot, do they also support his right to participate in the presidential debates? I would assume they don't, after all, the last thing they want is 2 people bashing Bush at the debates. Imagine if Bush had to debate against Kerry and Nader, he wouldn't be happy (I suspect he would decline to debate instead).