Challenge: birth control vs immunosuppressants

[Newbie2]

Ok. I guess what I’m not understanding is the Natural Law argument against ABC. ]Contraception is wrong because it’s a deliberate violation of the design God built into the human race, often referred to as "natural law

(from Catholic Answers tract)

It seems that we could substitute “Immunosuppressants” for “Contraception” in the above sentence, and a reasonable argument would be offered against suppressing the immune system.

How? Medically changing the function of the immune system does not affect life in a negative way, as can contraception. Contra=against, in this case against conception, life.

Even though we’re talking about body systems, it’s like apples and oranges when you’re talking about one system that produces life and the other that supports life.