sell out an oppressed people

[meramli]

Gene Sharp-From Dictatorship to Democracy

A few harsh realities concerning reliance on foreign intervention need to be emphasized here:
• Frequently foreign states will tolerate, or even positively assist, a dictatorship in order to advance their own economic or political interests.
• Foreign states also may be willing to sell out an oppressed people instead of keeping pledges to assist their liberation at the cost of another objective.

Can you explain what does 'sell out an oppressed people' mean and how can a plural (people) be used with 'an'? Thanks in advance.

 

[The Newt]

It means that they are willing to fail in their duty to assist the oppressed people, if they can benefit (usually financially) by doing so. "People" is treated as countable / singular in a few rare contexts, of which this is one.

 

[Parla]

To "sell out" is to betray.