Answer

I didn’t understand the question. The prohibition against emitting semen is not connected to fulfilling the commandment to be fruitful and multiply. Perhaps, according to someone who sees this as a kind of murder, one could argue that semen that is not capable of producing offspring does not involve murder—but then that has nothing to do with fulfilling the commandment to be fruitful and multiply. In Niddah 13b and Avodah Zarah 20b it implies that this is an adjunct of sexual immorality. The connection to murder is very tenuous.