Should I attend religious ceremonies in support of my friends?

I am an atheist, and I tend to stay away from any religious gatherings. I graduated high school 3 years ago, and one of my friends is graduating this year. He asked me if I would go to him to his baccalaureate ceremony, as his family and girlfriend cannot make it. This is a traditional religious ceremony held before the graduation of high school seniors. As an atheist, I object to the notion of God or that He had anything to do with the success of my friend and his classmates. My friend is semi religious, but it doesn't seem to be a big issue for him. Should I attend this ceremony in support of my friend or not? More generally, should an atheist attend religious gatherings in support of religious friends?