May I assume from your OP, wonderstuff, that you don't mind this advertisement www.thinkbox.tv/server/show/ConCaseStudy.1474, in which some white people (and a dog) are "in need of saving"?
Having read through your post, I searched through dozens of Salvation Army advertisements, and only found three that seemed to show predominately either white or black people, who were need of support (do you think showing people to be in need of support, is portraying them negatively?).
Of those three, one showed predominately white skinned younger people; one showed predominately black skinned younger people (perhaps the one to which you referred); and the third showed predominately white skinned people in a wide range of age groups.
On the other hand, my search found dozens and dozens of advertisement, each showing people with a range of skin colours, a range of age groups and a range of needs.
I think that the fact that your OP focused on that one advertisement, and interperatates a negative bias against race, says much more about you than it does about the Salvation Army.