Replace the question they ask you about chickens with a question of why they got (insert animals here) and see what kind of response you will get.
If I wanted to be nasty about it, I would tell them prove it if they think getting chickens would kill you, disease ridden and all that negativity that goes with it. Just say, being at the doctor's office, touching doorknobs would be worse than having chickens disease wise! AND getting something from chickens, the percentage is low and don't believe it if they say Oh, its a high percentage will get Avian Flu and so forth. Come on, its not like measles or chicken pox!