He's not promoting bigotry, merely stating he will not write a letter of recommendation. To promote bigotry would be to use the website to attack a religious or racial group for instance. He merely states he will not write a letter of of recommendation to anyone who does not believe in the "accepted" science on this subject. I disagree with the man, but I also support his right to not have to give a recommendation to anyone for any reason.
Saying that one is unfit to practice Biology if they do not accept the evolution of humans as fact is an attack. It is a kin to saying a person is unfit to practice Biology if they are Hispanic.