Lessig addressed that here:
Some worry that there’s something improper about using a corrupted
system to achieve corruption reform. Don’t we dirty our hands if we use
the money of the few to achieve a democracy for the many?
I understand that concern. I don’t agree with it. One might have said it
was wrong to use the racist system of American democracy to bring about
the rights of citizenship for African-Americans. I wouldn’t have said
that. Or one might have said it was wrong to use a sexist political
system to bring about a democracy in which women have the right to vote.
I wouldn’t have said that either. In my view, we work with the
democracy we have to make a more perfect democracy. And the only way
we’ll convince America that winning is possible is if we show America
we’ve got the resources to win.
It's a gradual approach, with the main event in 2016. You don't have to be convinced we can win yet, but if the issue ends up featuring prominently in more and more elections and calls for reform start to snowball in the media, I bet you'll probably come around. (No, mainstream media sources don't cover that stuff now. If political careers are on the line, of course they will!)
edit: One other thing, I don't think it's fair to say MaydayPAC will use the money it raises for "corporate-style lobbying." There's lots of that going on, and corporations spend a lot of money to influence legislators, but they haven't actually spent much, directly or indirectly through PACs, to finance campaigns. That money has come from wealthy individuals. I agree with you that a grassroots group should never expect to win real reforms in Washington by hiring lobbyists. But we're talking about airing commercials, sending ads to people, etc. Normal campaign stuff. Just get those campaigns to be more about the problem of money in Washington.