King Describes "the cruel irony of watching negro and white boys on TV screens as they kill and die together" (lines 38-39). The irony he refers to is that back home in America

King knows that through visual media, a deeper message can be achieved, and people of all ages can be more influenced to continue to have racist and social prejudices.

Explanation:

It is ironic and contradictory that a message of equality and unity is promoted using children, and in practice war and racism are promoted, that is totally misleading and unethical.

They must promote values from childhood, likewise an entire nation must be taught to be tolerant and sincere and to overcome all kinds of social and racial prejudices.