My claims are:
1) Nader proved he is just another politician.
2) as such his actions qualify him as a lousy one.
3) Nader is not to blame - just his Florida voters.
4) Florida: In democracies, the losing parties usually have just themselves to blame for irregularities.

1) Nader is just another politician (egomaniac)

Nader led a good campaign and raised the needed concern for important issues. A man of principles, at this stage, would realize that his candidacy stands no chance, and since the two candidates really differ on these issues, it would be best if his supporters choose the better (or lesser evil) of the two. A politicians would prefer matching funds to his party at the cost of oil drilling in Alaska. An egomaniac would prefer getting a million votes more, and the presidency determined by his voters over advancing his issues by having a president closer to them.

2) Nader is a lousy politician

imagine that a few days before the election Nader would've said: "My supporters are better informed than the average voter. I therefore encourage my voters in florida etc. to vote for the one they think is better among the 'two evils'. I also encourage my supporters in California, NY, Texas and other determined states to act according to their heart and vote for me". Such an act could have resulted in him getting more votes, while more battleground states would have gone with Gore: 2-0.

3) Nader is not to blame it's his voters

They knew their state is undecided and yet prefered this "moral" act (the quotes are for prefering the aestethic over the useful).
Gore is also to blame (see also the next point): He could have made a similar call to the one I suggested to Nader. battleground voters: you have just two choices, other voters: vote for the best candidate (and he would have still got 90+% of his voters).

4) Lousy organization loses more democratic elections than frauds

In 1996 frauds in "haredim" precincts helped Netanyahu. Who's to blame: "ha'avoda" which didn't put observers there. In Florida, good organization would have sent volunteers to every ballot in Palm beach to inform voters of the confusing ballots, and stop losing votes.