The poem asks a series of rhetorical questions about the number of times or years something must occur before a significant change or realization happens. Each stanza poses a question like "how many roads must a man walk down before you call him a man?" or "how many deaths will it take till he knows that too many people have died?". After each question, the answer is given as "blowin' in the wind", implying the answers are unknown but will reveal themselves over time.
68. There are many organizations devoted to making this world a better place for everyone. Be sure to give them some support. The next time you see them.