It basically means "caused to be." Here are some other examples:
I had him laughing at my joke.
I had him completely confused with my explanation.
The approaching storm had me concerned.
As you can see, in isn't required; in your example the meaning is "caused Paris residents to be in a heated debate." You could just as well say "had Paris residents debating heatedly," although it sounds a little stiffer.
There are similar usages. These examples have the meaning of "caused to do":
I had him run 20 laps around the field.
I had him go to the store for sugar.
I had him bring the beer for the party.
Then, "had him in" and "had him over" have the meaning of invited or required someone to come to a particular place:
I had him over last weekend. (This means that I invited him over to my house.)
I had him in to present his report. (This means I invited in to the office to present his report.)
The police had him in for questioning. (This isn't an invitation!)
Finally, there's a British idiom have someone on, which means to fool or tease someone. Americans will say pull someone's leg (a little less formal than have someone on) or shine someone on in the same situation.