Would people be wringing their hands if a women's team insisted on, and were told not to, wear a veil out of respect for their cultural habits. Worldwide, relatively few know what the poppy totem is meant to signify and similarly not a lot of people sympathise with the wearing of a veil. Both are practices designed for the "home market" and they otherwise leave people cold (to say the least).
Quite a few Muslim women feel obliged to wear a veil because it is the done thing, many of those brought up in the right circumstances feel they should wear a representation of a flower. Not wearing it does not imply indifference to death through military action, wearing it does not certify proper appreciation of every aspect of it.
FIFA's objection very possibly is to the interweaving of a national de rigueur ritual with an international competition. Saying this ritual is more worthy than others is of course of no interest beyond the group who support it.