Playboy, Miss America, and Maxim might be offensive and exploitive to some people and a great career opportunity to others. Personally, I was in a beauty pageant when I was younger. I had fun and did not feel exploited. I was never interested in Playboy, not that they were banging down my door.
It is very common for actresses appear nude in film, on stage, and sometimes even in magazines. It's strange that a sorority would have one policy for college students who appear in Playboy and not for actresses who appear nude.