They rob banks. They kill people. So, why, when they die at the end, does the audience mourn the passing of Bonnie and Clyde?
The cinematic counterparts of real-life bank-robbers/murderers/lovers Bonnie Parker and Clyde Barrow inspire a sympathy that was probably not felt for the real Bonnie and Clyde.
One superficial reason could be the physical attractiveness of the actors in Arthur Penn's 1967 movie Bonnie and Clyde. Faye Dunaway (Bonnie Parker) and Warren Beatty (Clyde Barrow) are both very attractive people (and neither really looks like his or her real-life counterpart). The sex appeal of the two actors could have inspired the sympathy felt by the audience. After all, how could you hate such beautiful people? And really, when they look this good, does it matter that what they are doing is wrong?
Another reason that the audience may have sided with Bonnie and Clyde in the movie is their "we're just common folk" attitude. After Clyde shoots the man who hung onto the car after the gang's first bank robbery together, he expresses remorse. He says that he would not have killed the man if the man had not been on the car. This shows that Clyde has a conscience. Another example of Bonnie and Clyde's "common folk" appeal is evident when they pick up Eugene Grizzard and Velma Davis (Gene Wilder and Evans Evans). They do not harm them in any way, despite the fact that the "Barrow gang" has killed several people. In fact, the gang buys the couple dinner, while being]quite pleasant and likeable. The audience sees that Bonnie, Clyde, C.W. (Michael J. Pollard), Buck (Gene Hackman), and Blanche (Estelle Parsons) are not just bloodthirsty maniacs.
The story of Bonnie and Clyde is also a love story, which adds to the appeal of its main characters. Bonnie and Clyde obviously care very deeply about one another, making them even more sympathetic. In fact, it could be argued that the love story becomes the center of the movie. Clyde even risks death and capture to reunite Bonnie with her mother (Mabel Cavitt). That shows true devotion on Clyde's part, and he even tells Bonnie's mother that they will be settling down in the area. They even meet their untimely ends together. The love story shows that Bonnie and Clyde actually had hearts.
The characters in Bonnie and Clyde are given so many redeeming qualities that the audience begins to relate to them. Perhaps the viewers have done something in the past for which they are ashamed, or perhaps the viewers have been in love before. Everyone can find something to relate to in the cinematic Bonnie and Clyde, making them the perfect antiheroes.