Question

What is the purpose of the sentence "I hope, sirs, you can understand our legitimate and unavoidable impatience" in the following paragraph?

I guess it is easy for those who have never felt the stinging darts of segregation to say wait. But when you have seen vicious mobs lynch your mothers and fathers at will and drown your sisters and brothers at whim; when you have seen hate filled policemen curse, kick, brutalize, and even kill your black brothers and sisters with impunity; when you see the vast majority of your twenty million Negro brothers smothering in an air-tight cage of poverty in