Rejecting the fact-value dichotomy need not imply that economics is not value-free. It is enough to realize that it is significantly value-relevant. For instance, it is perfectly value-free to claim that there can be no such thing as rational (opportunity cost-effective) economic calculation in the absence of private property in the means of production. However, if "ought" implies "can", such a claim automatically disqualifies building a rational socialist economy as a genuine moral duty, since there can be no duty to achieve the logically impossible.
Thus, while socializing the means of production in the pursuit of the "common good" can be regarded as objectively bad (no fact-value dichotomy), sound economic theory that leads to such a conclusion can safely retain its value-free (though not value-irrelevant) status.