The love thing was based on the movie La jetée who also inspired 12 monkeys. They use the word "love", but they are more talking about any kind of emotional bond. Those emotions are enough to drive someone even against reason. In the movie, they could have sent anyone in that tesseract, but without having a bond with the daughter, they wouldnt know how and when to pass the message. The people from the future used that love as a variable in their plan for cooper to communicate with his daughter. So people that stops at "love is stupid, its just a chemical reaction", well, not in time travel, the only reason he didnt lose hope and found his way is because of love. They chose the father and daughter based on that variable.