The Blues advocate taxes on individual incomes, the Greens advocate taxes on merchant sales; the Blues advocate stricter marriage laws, while the Greens wish to make it easier to obtain divorces; the Blues take their support from the heart of city area [..] Not every Blue or every Green citizen takes the "Blue" or "Green" position on every issue, but it would be rare to find a city merchant who believed the sky was blue, and yet advocated an individual tax and freer marriage laws.

Shouldn't it be rare for the city merchant to advocate for a tax on merchant sales and freer marriage laws?

Favoring individual taxes is mentioned as a blue preference, so it would not be rare for the "city merchant who believes the sky is blue" to advocate for it.