Cobranding with McDonalds

Is cobranding with McDonalds necessarily a good thing? I ran in a race this weekend to support breast cancer awareness. One of the sponsors for the race and on the back of the race shirt is McDonalds. It seems strange given that foods at McDonalds have been linked to cancer along with numerous other diseases. As marketers we face ethical issues every day - who do you market with? What does that portray about your company? Are you just seeking a partnership for the money or for true value being added to your brand? All of these are important questions to consider.