Dear Johnny,

Your question is similar to others like:

• It is okay to work at hotels that offer pornographic movies to its customers, or at convenient stores that sell such magazines?
  

It is best not to work at places that deal with these things; however if you offer no moral support for it, and do not intend to contribute to their sale in any way, then this may be seen as remote material cooperation in evil, but not sin.

If this could be an occasion to get the truth out, with the proper opportunity, it is always good to explain to people the morality of contraception and reasons why it is wrong.

Paul