There's no 75% tax in France. It never existed, and I don't think it will exist any day soon.
There's a 75% tax for income over 1 million euros per year. This means that if I earn 1,000,001 €, I pay the normal rate on 1,000,000 € (I don't know what it is, it might be around 30%, so let's say 30k) plus 75% (meaning 0.75 eurocents), the total being 30,000.75 cents. For 2 million euros, you'll pay 30,000 € + 75% × 1,000,000 = 105,000 €. It's the concept of tax brackets, and I know you have this in the US. Are the US a socialist country?
Moreover, France has a lot of billionaires, and the richest woman in the world – at the time I type this comment – is French. <http://en.wikipedia.org/w/index.php?title=Liliane_Bettencour...
In addition, there's a job in France called “tax optimizer”, I can't find a link, but in 2011, Liliane Bettencourt paid as much tax as a single Frenchwoman on minimum wage.
So I don't think tax is a problem in France for those who wants to be entrepreneurs. And do entrepreneurs really deserve to make that kind of money? Do they really work 300 times harder than their workers?
My 2 cents on it, the problem in France – and this is why Germany and the US are succeeding where France is failing – is the lack of support from the government towards small companies. Any labour law, tax law is made for giant groups like Dassault, Orange, Dannon, and so on...