Even if machines with true Artificial General Intelligence were created, their apparent intelligence would still be by definition artificial. The word simulation is a synonym and could be used to redefine AGI as Simulated General Intelligence.
Keeping that in mind, a machine that appears to be expressing emotions would only be the result of a series of complicated algorithms allowing a computer to assess the situation and respond in an intellectually appropriate manner based on external stimulus and conditions. Every possible action this machine could possibly make would be derived from a list of possible actions the machine is capable of, no matter how large the number of possible actions grows. The machine is still a series sensors, programmed instructions, and cycles of execution.
Destroying such a machine could potentially be the destruction of property if it wasn't owned by the person who destroyed it, but would it be murder? No.
A broken machine can potentially be rebuilt and reactivated if it is broken. It never really died; it was destroyed. A living being that is killed is really dead and cannot be rebuilt and made alive once again. These key differences lead me to agree with the previous answer and conclude that no, destroying an artificial intelligence without its consent would not be murder.