What kind of measures are needed?
Tony tries to calm Joe’s fears. He tells Joe that it may not be so bad. He may not need to take drastic action. He needs to survey Earth and mankind first, and from this data, decide on whether mild, severe, or drastic preventive measures are needed. But what does Tony mean by each of these levels of action? 
Tony takes offense at Joe for referring to population control as Tony's "dirty work". Tony prefers to call it "pruning", something which is good and necessary. But when you are the one who will be wiped out, it is hard to look on Tony's mission in a positive light. 
Tony and the Thonians aren't the only ones who think reducing the population is the answer to the world's problems. World leaders, the very wealthy, military strategists are trying to find ways to drastically lower the population. They often use "nice" words to talk about killing people off. The Israeli military called the attacks on Gaza "mowing the lawn". Tony calls wiping out whole cities "pruning". This kind of word or phrase is called a euphemism -- a mild or pleasant word or phrase that is used instead of one that is unpleasant or offensive. Joe is offended at the euphemisms. Are you?
 
Key words: http://www.dramaticlistening.com/DL035