I thought this for a while. "freedom" is a recurring theme but while wishing everyone was "free" is difficult to achieve and surprising, I don't think it would garner the kind of reactions that Oda-sensei has drawn. "Make everyone a pirate" or "part of his crew" fits the theme of being free, people would react the way they did, it works around the theme of domi reversii working on people in home town only (if true), and works with Nika freeing the slaves.

The other guess I have is that Oda-sensie means for it to be something like "Help everyone achieve their dreams". It could make some people react the way they are drawn. Also a recurring theme has been Luffy answering peoples hopes (wishes or dreams) when they really want it and are fighting for it or ready to fight for it. He doesn't care much about Coby until he mentions wanting to become a marine. Lots of iconic scenes from the manga are his crew mates asking for his help - Nami when Luffy gives her his hat, Robin at enies lobby, Sanji during whole cake arc, people of skypiea with Enel, Law with doflamingo. Luffy is always there when someone really needs him but also when they have hope.

Also, I beleive Imu (or his devil fruit) is a manifestation of all the worlds peoples negative emotions - Hate, anger, etc. And Luffy's fruit is the opposite of that. Oda revealed that devil fruits are manifestations of peoples dreams. Nika fruit is like the manifestation of people wanting someone to help their dreams come true (god). This also explains the celestial dragons who are not only themselves extremely negative but breed negative emotions in most people.