The last thing that you want your robot army to do, when asked "Are you exterminating the human race?" is answer "Yes." Public relations fiasco right there. You can't possibly go on Oprah often enough to make up for that one.
The solution? Make sure your robots know how to lie. Fortunately, there have been great strides in this very field recently. Some folks in Lausanne, Switzerland have been working in evolutionary robotics: they developed a pretty nice platform (the S-bots, shown in that link towing a terrifically tolerant tot) that have a number of general-use actuators and sensors. At the same time, they developed a decent computer simulation of those robots so that they could try out control schemes -- including multiple iterations of an evolved controller.
Note that they have both light rings (three colors of LEDs) and light sensors. The robots are each controlled by a neural network, the inputs for which include input from those sensors, and the outputs drive motors and other actuators. The weights of each node are determined by elements on a single long string, which is treated as genetic material for a genetic algorithm. They run the robots with a randomized genome, and those robots that "survive" (get to a power source) have their "genes" passed on to the next generation (that is, the next iteration of the experiment) Neural networks are a nice handy way to bridge the gap between genetic algorithms and programmed behavior, actually. Anyone who's interested in playing around with these techniques would not do badly to start off with something like this.
Anyway, I haven't read the paper too carefully, but it sounds like the deception involves the fact that the power source (the "food") has one colored light, and the robots can change color to that same color when they are there (thus helping the other robots with different genes) or they can turn off their lights or turn a different color to give themselves a larger relative advantage! Of course, robots that are attracted to both color lights would gain a further advantage, thus increasing the dominance of that particular strain: a bunch of them with the same set of mutations could effectively hide the power source from other robots.
There's more coverage, with more videos at Singularity Hub. If you're interested in the bots themselves, the older swarm-bots have a page here, and the newer version is over here. The papers there are pretty approachable for technically-minded folks not in robotics, I think, but are not quite to the level of general consumption. Good stuff.
I guess the only remaining question, then, is that, having now learned to lie, will robots ever learn ... to love?
The answer is no.