Just like Proposition 86 in california was fought:
http://www.smartvoter.org/2006/11/07/ca/state/prop/86/
How they did it: They made sure the consumers knew, to do this they posted signs at most liquor stores, signs explaining the proposition and why it would be bad for both the consumer and the business. Gosh, I must have seen that sign at least once a day... Anyhow, I guess the only way to fight .xxx would be to encourage webmasters to add anti-xxx banners on their adult sites to get the surfers involved. Because fighting prop 86 didn't just need the store owners, it also needed the customers.