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The author concludes that the proposed program - young people providing service to correct current social ills - should not be implemented, because government service should only be compelled in response to a direct threat to the nation's existence.
So obviously, the assumption is that the current social ills do not constitute a direct threat to the nation's existence. That was easy to figure out.
But there were two tricky choices: (B) and (E). (E) says "some" of the current social ills aren't a direct threat. But that doesn't seem to rule out the possibility that some are in fact a threat, in which case, the conclusion doesn't make sense. For example, if the social problems in education aren't a direct threat but the problems in housing are, then the author cannot say the service shouldn't be used. As for (B), I found it to be rather extreme, but still felt it was the best answer here.
Please help with this one.

Thank you.

B is incorrect because the stimulus says nothing about whether or not the country in under foreign attack. We have no way of telling.

As for E, it's not exactly a perfect prephrase choice, but if the 2 social ills mentions ARE NOT threats to the nation's existence, then it must be true that at least some of the social threats pose no threat to the nation's existence. If this is false the argument falls apart.