I've been thinking about this lately.
I know in some wars it was considered wrong to kill medics or killing someone retriving wounded. But how about other men who performed other duties than fighting?
I tried to google this and found another thread somewhat discussing the subject, but does not really answer my question.
(P.s english isnt my first language, be gentile)
An important thing to remember is that soldiers in the 17th and 18th centuries could only rarely aim at specific enemy soldiers with any realistic expectation that they would hit their intended target. Even people who give us detailed descriptions of combat, like Joseph Plumb Martin, often express uncertainty as to whether they were able to land killing shots even when carefully aiming, due to the distances involved and the smoke and confusion of battle.
In all the reading of soldiers' accounts I have done, I have seen no reference to soldiers being mocked or stigmatized for shooting musicians. While proving a negative is impossible, there seems to be no evidence to support the existence of a stigma.
Can I add the follow up question - what are flute guys called in contemporary (say, 17th-19th century European and North American) sources? My instinct would imagine piper, but maybe this is too specific and limited only to bagpipes? I have no idea, but it's something I never knew I wanted to know until now.
This is not a direct answer to your question, excuse me, but rather a clarification of the term standard bearer as I've come to understand it.
The men listed as standard-bearer under the English 1338 campaign to Flanders were few in numbers. Excluding some garrisons, retinues and some temporary Welshmen, the English army included: 5651 men in total. These standard bearers I have come across were knights and veterans of former campaigns, holding position of power and titles.
11 standard bearers
46 banneret
235 knights
1,449 men-at-arms
79 hobelars and armati
1,254 mounted archers
2,478 foot archers
93 vintenars
6 centenars
For example Sir Guy Brian, served in the Scottish campaigns 1327 and 1337, Flanders 1339, Calais 1347 before becoming the king's standard bearer in 1349. Later he was captain of 20 mounted archers 1359. In 1369, he lead 29 men-at-arms and 30 archers. In 1369 he was appointed Admiral of the Fleet and his name appear several times in the muster rolls after that between 1370-79. In a handful of different instances, he leads a combined number ~1000 soldiers during this period. His birth is not clear, but it's believed to be around ~1310 and he died august 1390. He obtain numerous titles and he would probably be taken for ransom rather than killed. If I've misunderstood you, then please correct me.
The Peerage
The medieval inventories of the Tower armouries 1320–1410
Muster rolls, 1369 - 1453, The National Archives (TNA).