Let's define moral realism as the view that there are objective moral truths. There are many different arguments for and against the view of course. However, recently there has been a lot of work on evolutionary "debunking" arguments against moral realism. We can sketch the argument as this:

ur moral beliefs are explained by evolution by natural selection.
However, evolution by natural selection is an "off-track" process; it is not concerned with truth but reproductive success.
Off-track processes do not produce justified beliefs.
Therefore, our moral beliefs are unjustified.

Consider an analogy. Suppose that there is a species of plant A which is poisonous and another mimic species B which is not. Likewise, suppose A is found 90% of the time in our environment whereas B is found 10% of the time. If you encounter a plant and you don't know whether it is A or B what should you believe to maximize your reproductive success? Clearly, you should believe the plant is A. In this instance, your fitness is greater if you form false beliefs rather than true beliefs.

Is this argument sound? Why or why not?