I couldn't think of a better way to word this so sorry if it's confusing. I'm specifically curious as to any ethical concerns raised by writers when a new weapon was introduced onto the battlefield but my question could apply more broadly.
For example, when gunpowder weapons were introduced onto Western battlefields were there any writers who opposed this on ethical grounds? (and advocated for older technologies)
Not exactly what you're asking, but as close to this as I can think of an example being. In 1595 England officially retired the longbow from its military and switched over to only using gunpowder weapons for ranged warfare (they also swapped from halberds to pikes for melee weapons). This was not a sudden shift whereby one day England used only bows and the next only guns, this had been in the works for some time and gunpowder weapons had been in use in the English army for centuries. This act was more significant in that it ended the longbow rather than that bringing on the era of gunpowder.
The thing that's really interesting was there was a significant backlash against this change from members of the English elite. Several pamphlets were published decrying the decline of English archery and declaring that if only the traditional practice and training were reinstated the longbow would prove the superior weapon. Others wrote in praise of gunpowder and welcoming the end of the longbow.
Thomas Esper's article 'The Replacement of the Longbow by Firearms in the English Army' in Technology and Culture, Vol. 6, No. 3 (Summer, 1965), pp. 382-393 has a lot more detail on the specific authors, who they were and what they argued.