Is someone paying them to give their readers inaccurate information? I'm inclined to doubt that explanation, but why does the paper keep using this description when it is so obviously not true?

The issue came up in the context of a discussion of the agenda of the Democrats in the House of Representatives. The article notes differences between House Democrats and President Obama and trade, and then tells readers;

"Republican leaders are preparing legislation that would grant Obama broad authority to finalize one of the largest free-trade pacts [the Trans-Pacific Partnership] in the nation’s history."

The Trans-Pacific Partnership (TPP) is far from a "free-trade" deal. It actually will increase some protection in some areas, notably stronger and longer patent and copyright protection. Most of the deal is devoted to creating a uniform and largely business friendly regulatory structure. It creates special courts for businesses to sue governments outside of the normal judicial process. Since most trade barriers between the parties in the pact are already low, it will do little to reduce formal barriers to trade.

It is difficult to see why the Post cannot simply refer to the TPP as a "trade agreement," or even more accurately a "commercial agreement." It could save its praise of the pact for the opinion pages.