I don't think it's possible to legitimize bitcoin in the eyes of governments whose operation rests on constantly inflating the money supply. And I'm unconvinced that the people who worry about paying taxes will see bitcoin as legitimate when government is publicly decrying it.
Governments subsist on the wealth and productivity of their citizens, not on any currency.
Showing that businesses can use Bitcoins and increase their wealth while paying the appropriate taxes will get governments behind Bitcoin. They already have small amounts of people working hard to anonymously exchange using USD, they don't really care if a small amount of people will do the same with Bitcoin.
People arguing that tax paying USD businesses are going to become tax evading Bitcoin businesses is what will get a government to stomp its foot down.