Sean Penn is slamming cynics who have criticized his recent trip to Haiti. In January, the actor, 49, brought 11 doctors to the earthquake-hit nation, where he also helped establish a private Haitian relief organization. But some have argued that celebs like Penn should stay out of aid efforts, insisting that stars use tragedy merely to rebuild their public image (Penn recently went through a divorce with actress Robin Wright). Critics also say that stars’ efforts are hypocrtical: They complain about the injustice of others, critics say, only to return to their holiday homes and lavish lifestyles. But in an interview this weekend on CBS News’ Sunday Morning, Penn says he ignores the negative chatter. “I guess I’ve been so away from it all– and our tent camp in Haiti that I haven’t had an awful lot of time to pay attention to them,” he says. “You know, do I hope that those people die screaming of rectal cancer? Yeah. You know, but I’m not going to spend a lot of energy on it.”