I was recently confronted with a project that conflicts with my personal beliefs. It doesn't happen that often, but often enough where I have to sit down periodically and determine what work I am and what I am not willing to take on. I'm a firm believer in the notion that there should not be a separate set of ethics for things personal and professional. This generally makes the decision-making process a little easier, but it can also make me question, in a healthy way, the validity of decisions made on either side.
I took this project on, but it still bugs me. It's not anything off-color or political. I do wonder how other illustrators handle things like this, though.