It doesn't (any more)
As of MacOS 10.14.4 (released Mar 25, 2019), "freedom fries" is no longer a search keyword for the ?? french fries emoji.
I checked before and after upgrading from MacOS 10.14.1 (released Oct 30, 2018) to confirm that this was a recent change.
The removal was plausibly a result of this Stack Exchange thread (posted Nov 2, 2018). I can't find anybody else on the internet drawing attention to this keyword until this question was posted. This question got over nine thousand views and was a Stack Exchange "Hot Network Question", and then I emailed Tim Cook for good measure.
“Freedom Fries” used in Apple’s emoji picker
Date: Fri, 2 Nov 2018 12:39:08 -0400
To: Tim Cook <email@example.com>
From: Jeremy Banks
I just wanted to draw your attention to the fact that the phrase “freedom fries”, a potentially offensive and dated political meme, is one of the search terms used by Apple’s emoji picker. (It’s listed in the CharacterPicker.plist file.)
Please consider removing this keyword.
- An Apple User