Writing in the New York Post, Bob McManus explains, in his view, "Why liberals just love to set terrorists free." He's entitled to his opinion and I don't find it necessarily unpersuasive. However, I have my own view, which I will now, with your permission, share with you.
I believe progressives love to free terrorists because they have the sneaking hunch the terrorists were justified in doing the evil things they did. If liberals don't always agree with terrorists' extreme actions, they agree with many of their grievances.
Liberal/progressives start with the notion that our society is wrong, oppressive, unjust, and more than a little evil. To them the glass is always at least half empty. Radical means are justified to right its wrongs.
Conservatives are comfortable with our society which they view as decent, free, just, and pretty darn good. To them the glass is at least half full, maybe more. Therefore radical means are not justified, and terrorists should not be freed.
The appeal of Trump's "Make America Great Again" slogan to conservatives is his promise to undo the radical things progressives have done in pursuit of equal outcomes for all. Conservatives know equal outcomes are inherently unfair as they are not proportional to the recipients' efforts and accomplishments.
Bottom line: Liberals view individuals as pawns, without agency, buffeted hither and thither by cruel fortune. Conservatives view individuals as captains of their own fate, essentially meriting in most cases what they end up with, good or bad. Pawns don't deserve punishment, free individuals who screw up do.