You're implying the farmers and workers would be better off if those low-paying jobs didn't exist, which is obviously not the case, as the fact that they took those jobs indicates it was better than the next best job available to them.

This same fallacy applies to criticisms of FoxConn factory jobs in China or construction jobs by imported labor in Dubai.

To you, the jobs are terrible, but to the people who get them, they are a significant improvement over the status quo. Eliminating those low pay jobs, by mandating higher paying jobs, would not lead to a one-to-one substitution of those "bad" jobs for what you consider to be good jobs. It would replace a huge number of low paying jobs for a small number of high paying jobs, leading to many going without.

Fundamentally you're making a fallacy of misattributing the cause of the poor conditions those workers experience to the people offering them their job, when in reality the cause is their low skill level, combined with the low capital concentration levels in their country, making their labor worth little.